10 Fantasy Baseball Players to Buy and Sell for Week 4

The secret to Mike Trout's success is apparently in the juice (no, not the bad juice).

There is no doubt among sane human beings that Trout is both the best real-world baseball player and the best player in fantasy. There's a reason he is drafted first overall every year, and this year, his performance is making that decision look like even more of a no-brainer. On Sunday against the San Francisco Giants, Trout slugged his league-leading ninth home run of the season, and he made it look way too easy.

That puts him on pace for 66 round-trippers this season, and upon returning to the dugout, Trout needed to refuel because he is, in fact, a human being and not a robot.

One can only imagine what's inside this special beverage, but whatever it is, it's helping to make him even better. In 101 plate appearances, Trout is batting .306/.406/.682 with those 9 dingers, 17 RBIs, 18 runs scored and 3 stolen bases. His walks are down a bit (13.9% walk rate, compared to 17.0% last year) and his strikeout-rate is up slightly (17.8% to 18.8%), but his isolated power (ISO) is the highest of his career (.376) as is his wOBA (.456) and wRC+ (194). His hard-hit rate of 46.3% is also a career high, and he's hitting ground balls at the lowest rate of his career (31.3%) while hitting a homer on 26.5% of his fly balls, also a career-best clip.

If you have Mike Trout, you ain't trading him. If you want to acquire Mike Trout, you're paying through the nose to get him. The only trade that makes sense for a Trout owner is to get at least something like Mookie Betts or Jose Altuve in return as well as a top-flight starting pitcher. Otherwise, owners are keeping Trout and enjoying the ride.

Here are nine other players to buy and/or sell (or hold) for Week 4.

Buy Johnny Cueto

Anyone who left Johnny Cueto for dead after a tough 2017 made a mistake, apparently.

Last year's main issue for Cueto was walks, of which he gave up too many. In 2017, he posted a career-high walk-rate of 8.2% and 3.24 walks per nine innings (BB/9). This year, those numbers are back within his career norms, with a superb 4.3% walk-rate and 1.38 BB/9. In four starts for the San Francisco Giants this year, Cueto is 2-0 with a 0.35 ERA, 2.19 FIP, and 3.72 xFIP. In 26 innings, opponents are hitting just .149, and his 0.65 WHIP is at a career-low level, too.

With velocity diminishing on his fastball (just 90.5 miles per hour on average this season, down from 91.3 miles per hour last year), he's throwing that pitch less (just 44.3% of the time), while using his curveball (6.6%) and changeup (25.1%) more. Cueto has always had a five-pitch repertoire, and he is using some different arrows in his quiver to get the job done.

Normally with a pitcher who has a slowing fastball, you'd probably want to sell. But for Cueto, he's proven to be an All-Star pitcher in the past, and this seems like a case of an ace pitcher figuring out a way to get the job done differently. Add Cueto to your rosters without worry.

Sell Ryan Flaherty

When the Philadelphia Phillies cut Ryan Flaherty just before the end of spring training this season, it was the right move. After all, in his career, the 31-year-old infielder had a slash line of .223/.294/.362 with 36 bombs in 470 games and a wOBA of .289.

But when one glances at the National League leaderboards as the calendar creeps later into April, the Atlanta Braves' third baseman is defying all logic by leading the Senior Circuit in bating average (.362) with great marks in on-base percentage (.471) and slugging percentage (.500). He's walking in 15.7% of his plate appearances, a career-high by far, and is sporting a .420 wOBA that no one saw coming.

If you happened to add Flaherty as a free agent, you've had your fun. Now's the time to sell. Get something for him, because this is completely and totally unsustainable. His batting average on balls in play (BABIP) of .444 is going to normalize, and he doesn't have the power (just one home run this season) to make up for a batting average that is going to start dropping any day now.

Buy Gleyber Torres

The next big rookie has arrived.

Gleyber Torres has been called up to the Majors and will play second base for the New York Yankees. He has just one game under his belt thus far, but his talent is immense. In 14 Triple-A games this season, Torres was batting .347/.393/.510 with 1 homer, 11 RBIs and a wOBA of .404. He's not a power guy, with a single-year career-high of just 11, done in 2016, but he's a high-average, on-base guy who is eligible at a thin position and can give fantasy owners some help in some important categories.

You might want to ride him on the bench for a bit until he gets comfortable, but he should be added in all leagues if he hasn't been already.

Sell Sonny Gray

Folks, it appears as if the old, good Sonny Gray may be gone from our lives forever. And if you can find an owner willing to take a chance on a big name, do it.

Gray has made four starts this year and in three of them, he's failed to get through the fifth inning. He has walked 6.06 hitters per nine innings this season, up from an already-high 3.16 last year and 3.23 in 2016. In fact, 2015 was Gray's last "good" season, when he had an ERA of 2.73 and was worth nearly four wins above replacement as a starter for the Oakland Athletics.

This year, his ERA is 8.27 with a FIP that indicates some bad luck (4.32) but is still not good. His xFIP of 5.21 suggests his peripherals are not outperforming his baseball card stats. Gray still throws hard (93.0 miles per hour) but hardly ever throws his fastball anymore (a staggeringly-low 34.5%) and is instead relying on a cutter and curveball more.

It isn't working, Sonny. Do something else.

Sell Matt Harvey

Speaking of starting pitchers to give up on...

After a 2016 season in which Matt Harvey posted a 6.70 ERA, 6.34 FIP, 5.39 xFIP and an fWAR of -0.8 in 18 starts, he's followed that up with a 6.00 ERA, 4.73 FIP, 3.63 xFIP in four starts for the New York Mets this season, a performance that has earned him a trip to the bullpen.

Harvey has gotten a little unlucky, with a BABIP of .324 that has helped hitters bat .294 against him, and he's reduced his walk rate from an insanely high 10.9% last season to 4.3% this year. But his fastball velocity continues to plummet (92.5 miles per hour on average in 2018, down from 93.8 in 2017 and 94.5 in 2016). No one is chasing pitches out of the zone against him, with a swing rate of just 23.4% on pitches outside the zone, a career low by a wide margin.

And now, he's out of the Mets' starting rotation. You probably can't get anything for him if he's on your roster, so sell him for peanuts or drop him altogether.

Buy Nick Pivetta

As for a pitcher you should be gobbling up as quickly as possible.

Nick Pivetta probably isn't going to pitch this well over the course of the entire 2018 season, but it's pretty obvious he's going to be a very valuable arm in fantasy. In five starts, he has a 2.57 ERA, 2.66 FIP, 3.11 xFIP, with a 25.5% strikeout rate. The biggest improvement in Pivetta has been his reduction of walks (3.6% walk rate so far), which has allowed him to pitch deeper into games and pile up innings (28.0).

And in case you're wondering if this is fluky, Pivetta throws in the mid-90s with some nasty breaking stuff that is pure swing-and-miss material.

Everything checks out here, and Pivetta is worth buying-high.

Hold Franchy Cordero

Franchy Cordero has been one of the more entertaining players to watch so far this season. In 40 plate appearances, the San Diego Padres' center fielder is batting just .243 with a .282 on-base percentage. But his slugging percentage of .514 is indicative of the kind of raw power he possesses.

Cordero has hit three bombs this year, with an ISO of .273 and wOBA of .343 that shows some great potential. He is striking out too much (32.5% strikeout rate) and walking too little (5.0%), but Cordero is a rookie who is learning on the fly. He also hits the ball hard just about every time he makes contact, with a hard-hit rate of 56.0%.

He's a brutal defender, and there is still much work to be done. But he's worth holding onto to see just what's there. Try to stash him on your bench for as long as you can.

Sell Ken Giles

After a postseason in which he was wholly unreliable as the team's closer, the Houston Astros' Ken Giles appears to have lost that job. In the team's last save chance, it was Chris Devenski pitching the ninth inning and getting the save in a 4-1 Houston win. The team said this week they were concerned about a possible back injury for Giles, but after Sunday's game, his fifth-straight scoreless outing, manager A.J. Hinch said it was the best Giles has thrown in the last year.

His overall numbers look fine this season, with a 2.57 ERA and 2.30 FIP. But his xFIP of 4.48 is likely because he has struck out just three batters in seven innings. He still throws in the mid-to-upper 90s, and opponents are only hitting .222 against him with a WHIP of 0.86.

Nevertheless, it appears as if Giles is out as the team's closer, at least temporarily. Sell him if you've got him unless your league rewards holds.

Buy Keynan Middleton

If you're looking to add a closer on a good team, then snatch up Los Angeles Angels closer Keynan Middleton, who has beaten out Cam Bedrosian and Blake Parker for the closer's job in Anaheim.

Keynan throws hard (96.2 miles per hour average this year) but has made some changes with pitch selection that has helped him a bit. He's still throwing his fastball more than any other pitch (64.9%), but he is utilizing his changeup a lot more compared to last year (from 2.4% to 9.8%) and has reduced the usage of his slider (35.0% to 25.3%). He now has five saves on the season for the Angels, with a 2.08 ERA, 3.46 FIP and 4.11 xFIP while striking out 23.5% of hitters.

Keep an eye on the closer situation in L.A., but for now, Middleton is the reliever to own.