Well, we're three weeks in, which means we find ourselves nearing one of the most important parts of the fantasy baseball season. Are hot starts legitimate signs of breakout performances? Are cold starts just a result of a small sample size, or are they warning signs?

For the most part, it's too early to overreact. Most MLB teams have only played 18 or 19 games at this point, which is less than 12% of the regular season. However, you will find several owners ready to push the panic button already.

Perhaps you're one of these owners -- it happens to the best of us. If you're not sure whether you should hold or fold on a player, that's why we're here.

The following 10 players have seen a perceived change in their fantasy stock, and we'll attempt to decipher which ones warrant taking action on this early. Some may seem premature, but that is the goal -- to be ahead of the rest of your league.

Buy Carlos Martinez

As the 13th pitcher off the board (on average) in ESPN leagues, it is fair to say that Carlos Martinez's first three weeks have been a disappointment for owners who invested in him. Most expected a breakout from the 25-year-old entering his third season in the St. Louis Cardinals rotation, but through three weeks, Martinez is the owner of an 0-3 record and a 4.76 ERA.

A deeper look at Martinez's peripherals suggest he has pitched much better than the base numbers indicate. In fact, outside of some control issues, Martinez has actually pitched better than he did last year.

His strikeout rate is currently at 29.8% this year (12th-highest among starting pitchers), which is a huge rise from the 21.5% he posted in 2016, while his xFIP (3.22) and SIERA (3.23) are both down from last year's marks. His 13.3% swinging strike rate ranks in the top 15 of starting pitchers, and opponents have also posted just a 71.1% contact rate against him, which would be the best mark of his career.

His walk rate (10.6%) is up, but the majority of that came in one game in which he was effectively wild against the New York Yankees, striking out 11 and walking eight. He has just three walks in his other three starts, as opposed to 20 punchouts.

He also has been a victim of some bad luck, as opponents have posted the 10th-highest BABIP (.351) against him, up from his career mark of .312, while he has stranded just 69.2% of base-runners, down from a career strand rate of 76.3%.

Martinez has been absolutely nasty to start the year, the results just don't quite back it up yet. Give him four more starts, and you probably will have forgotten about the "slow start." If his owner is ready to panic, be sure to take advantage.

Hold Manny Machado

Manny Machado has seen his batting average on a steady incline over the past three seasons, to a career-best .294 mark last season. He was able to do so without sacrificing any power, posting his second consecutive season with 35-plus homers. His breakout season, combined with acquiring shortstop eligibility made him one of the most highly-coveted assets this spring, as his average draft position vaulted all the way to the seventh-highest player in ESPN leagues.

After a very quiet first three weeks that have seen him post an uncharacteristic .206 batting average and .397 slugging percentage, some owners might be worried that they reached too far for Machado. Let's take a look at the underlying numbers for some answers.

Machado's struggles in the batting average department can probably mostly be explained by some bad luck on balls put in play. His .213 BABIP is among the league's worst marks and is a far cry from his career .307 mark. That is especially surprising when you consider his 46.0% hard hit rate, which is up from a career 32.3% mark. No other player in the bottom 30 in terms of BABIP has a hard-hit rate above 40.0%.

His seventh-ranked average exit velocity of 95.5 miles per hour further backs up the fact that he's been locked in at the plate, and it is only a matter of time until his hard-hit balls start finding holes rather than gloves.

A look at his batted ball profile, courtesy of FanGraphs, suggests he could see another small step forward in the power department, as well. In addition to a boosted hard-hit rate and average exit velocity, Machado has posted a ground-ball rate that would be the lowest of his career, along with a fly-ball rate that would be the highest. Despite this, his fly-ball-to-home-run ratio is the lowest it has been since 2013. That should correct itself over a larger sample size, so a power binge could be coming soon.

Sell Lorenzo Cain

Lorenzo Cain has been one of the few bright spots for a struggling Kansas City Royals lineup, posting a .333 batting average. Cain was a staple on the feel-good World Series appearances in 2014 and 2015, and was a usable fantasy asset, so owners might think his hot start is a return to relevance for the 31-year-old outfielder.

While it is certainly possible that Cain is able to bounce back to something resembling his 2015 form if he can stay healthy, him singling his way (16 of his 20 hits have been singles) back into our hearts seems more like a mirage.

For starters, Cain has a .426 BABIP through his first 17 games, which is the sixth-highest mark in the league and is well above his career .347 mark. Among the other 13 players who have a BABIP above .400, none have a lower hard-hit rate than Cain's 21.3% mark and only one has a ground-ball rate lower than his 46.8% mark. Cain also boasts an unsustainably high infield-hit rate of 22.7%, which ranks third in the league and is well above his career mark of 10.2%.

This isn't to say Cain can't be useful, but rather that the way he is going about it thus far is not sustainable. If you can get an owner to buy into the .333 batting average, see what you can get for the aging outfielder.

Buy Luis Severino

Through the first three weeks of the season, no starting pitcher has a better xFIP and SIERA than -- you guessed it -- Luis Severino. He also boasts the third-highest strikeout rate (35.5%), has induced more ground balls (50.0% ground-ball rate) and has displayed much better control, posting a 2.6% walk rate and 0.80 WHIP that would both easily be career bests.

Despite his dominant peripherals, Severino is the owner of just a 4.05 ERA. The only other three starters with an xFIP or SIERA below 2.00 have ERAs of 0.44, 0.91, and 1.73. What gives? Well, Severino has really struggled to strand base runners thus far, posting a 57.7% left on base percentage that is the second-worst among qualified starting pitchers and is far below his 72.6% career mark.

There's still some risk attached to Severino, as a pitcher who is susceptible to home runs and pitches at Yankee Stadium, but everything in his peripherals point towards a talented hurler ready to take the next step in his career.

Sell Evan Gattis

This is nothing against Evan Gattis the player, but rather the role he appears poised to occupy for the Houston Astros this season. Through Houston's first 19 games, Gattis has appeared in just 12 -- three of which have been as a pinch hitter. He has hit in the top-five of the lineup just three times. With playing time being split between Gattis, Brian McCann, and Carlos Beltran, it would take a trade or injury to clear up more playing time for Gattis, who is on pace to start just 77 games for Houston this season.

While he will likely continue to be one of the most valuable catcher options on a per-game basis, it will be almost impossible for him to reach the top-seven catcher status (especially in points leagues) he was drafted for if he plays just 77 games. It took him 128 games to rank fifth among catchers in points in 2016. If you can find an owner who still values him near the spot he was drafted, sell him while you can.

Hold Trevor Story

Trevor Story's start to the season has been a near polar opposite of his red-hot beginning in 2016, as he is the owner of a pathetic .169 batting average. As such, you will likely receive low-ball offers from leaguemates who will cite his breakout rookie campaign as a fluke. While there have been some apparent changes in his swing that could hint at a dip in batting average this season, it is not going to be nearly as drastic as the early results would suggest.

For starters, the already fly-ball-happy Story has raised his fly-ball rate from 47.1% last season to a ridiculous 72.2% this season. His contact rate is also down from 72.9% to 61.9% to start the year. If those numbers stay anywhere near those levels, it will be very hard for Story to repeat the .272 batting average from his rookie campaign.

Story's hard-hit rate is also down a bit from last year's impressive 44.9%, but his average exit velocity of 93.3 miles per hour is much higher, ranking 12th in the majors. If he continues to hit the ball this hard while launching fly balls at such a ridiculous rate and playing half of his games at Coors Field, Story should have no problem exceeding last year's 27 home runs. Assuming he gets some better luck on balls put in play (.219 BABIP), his batting average will likely rise to something a lot closer to last year's .272 mark than his current average.

Sell James Shields

Through three weeks of baseball, only nine starting pitchers have a better ERA than James Shields, whose ERA sits at a sparkling 1.62 mark after posting a horrendous 5.85 mark last year. However, his 5.18 xFIP is much more in line with last year's 5.21 mark and screams that regression is coming.

It really doesn't take much effort to identify that Shields has clearly benefited from good luck. He is one of just two starting pitchers to have a 100% strand rate through the first three weeks, which is clearly unsustainable (the highest strand rate among qualified starters last season was Jon Lester's 84.9%). Opponents have also posted just a .150 BABIP against him, which is the second-lowest mark among starting pitchers.

Shields has also allowed a 58.1% fly-ball rate and just a 27.9% ground-ball rate, both of which are way worse than his career marks. His walk rate is also up, to what would be a career-high 14.5% rate. All things point towards another down year from Shields, except for his clearly unsustainable BABIP and strand rate.

If you are a Shields owner and can get anyone in your league to pay for him based on his career pedigree, take advantage now. It won't be long until the bottom falls out and Shields starts to resemble the pitcher who nearly posted a 6.00 ERA last year and not the incredibly lucky pitcher who has a sub-2.00 ERA through three starts.

Buy Lance McCullers

A popular sleeper before the season started, Lance McCullers has done nothing to disappoint thus far, posting a 3.38 ERA and an impressive 11.63 strikeouts per nine innings. So, are we to buy high on the already-hyped starting pitcher? While nontraditional, that is exactly the situation we are looking at.

McCullers has been unbelievable thus far, posting the league's ninth-highest strikeout rate (30.2%), as well as the ninth-highest strikeout-to-walk ratio (24.8%). While his 3.38 ERA is certainly impressive, it is nothing compared to his fifth-ranked 2.17 xFIP. His opponents have also posted a .310 BABIP against him, which is a top-30 mark among starting pitchers.

The injury concern will always be there for McCullers, who has yet to pitch 130 innings in his major league career, but the peripherals certainly check out. if you can find an owner who still values him based on his middling 3.38 ERA and the well-documented injury concerns, be sure to take advantage. McCullers has legitimate ace-level stuff, but can still be had at a discount thanks to his track record and injury concerns.

Sell Ender Inciarte

Ender Inciarte has seen his ESPN ownership rise to 63.8% due to his hot start, as he has displayed a unique power-speed combination, putting up four homers and two stolen bases through the first three weeks while hitting leadoff for the Atlanta Braves. However, he has maintained just a .238 on-base percentage while hitting atop the lineup, thanks to a .208 batting average and a minuscule 3.8% walk rate. If he keeps those numbers up, he won't occupy the leadoff role for much longer.

Inciarte's power has also been bloated by a 20.0% home-run-to-fly-ball ratio. His previous career high was a 5.1% mark in 2015. Considering his 25.4% hard-hit rate and 33.9% fly-ball rate, that ratio seems highly unsustainable.

His early success in the power department has led to Inciarte developing some troubling plate discipline issues, as the outfielder has been just hacking away. His 55.3% swing rate is the 14th-highest in the majors, while the 44.7% of pitches outside of the zone that he has swung at is the fourth highest.

If you can sell Inciarte based on his hot start in the power department and his role as the leadoff hitter, do so now. He's already matched his career high for home runs and will likely level off in that department soon, and his impatient, swing-happy approach at the plate is not indicative of a successful leadoff hitter.

Add Adam Wainwright

Adam Wainwright's ESPN ownership is down to 56.8%, as he has been one of the most frequently dropped pitchers in the league. Well, considering the 35-year-old's 1-3 record and 6.27 ERA, that really isn't that surprising.

While his early ERA isn't encouraging, his 3.07 xFIP is his lowest mark since 2013 and suggests better times may be ahead for the aging hurler. A lot of his early struggles can be traced back to an unlucky BABIP against of .467, which is well above his career .297 mark and is the highest in the majors. His strand rate is also down from a career 74.6% mark to 66.3%, which further suggests he's been a victim of some bad luck.

Wainwright's stuff has certainly been there -- his current 9.6% swinging-strike rate would be his highest mark since 2007, while opponents have posted just a 79.1% contact rate against him -- the lowest mark since 2010.

If Wainwright's owner dropped him in frustration after his first few starts, take a flier on him and hope the peripherals start to shine through into his base numbers.