We're roughly a month and a half into the 2019 season, and it's about that time when slow starts become more than just a slow start -- or, vice-versa, when we need to start taking seriously that random hot stretch we've been dismissing as a fluke.

Some important statistics -- such as strikeout rate and walk rate -- can begin stabilizing as early as a few weeks ago while batted-ball stats like ground-ball rate and fly-ball rate are becoming more telling with each passing day. In short, we can pull some actionable information from what has happened so far, even though 40 or so games isn't a huge sample size by any means.

Despite the incredible growth of advanced stats in baseball, most fantasy leagues still put a ton of value in traditional statistics such as RBI and batting average. As we know, those stats don't always paint an accurate picture of how a player is truly performing. Advanced metrics allow us to see through the box-score rubbish and find out what's really going on. This can be incredibly useful for fantasy purposes as those metrics can clue us in on who is playing better than their traditional numbers suggest or -- on the other hand -- whose success is a smoke-and-mirrors act.

Let's look at five hitters who are likely being undervalued in season-long leagues due to their underwhelming performance in traditional stat categories. There's a good chance you can get these players for less than they're actually worth, bolstering the rest-of-season outlook of your fantasy squad.

Matt Carpenter, 1B/3B, St. Louis Cardinals

Last season, Carpenter ranked 11th in baseball in wRC+ (138). So far in 2019, he sits eighth in wRC+ ... among hitters on the St. Louis Cardinals.

Carpenter's 2018 campaign was something else. He started slowly and then went absolutely nuts over the season's final four months, posting a .952 OPS from June 1st on (h/t to our Tom Whalen). Sure enough, he's been bad early on again this year, carrying a .293 wOBA and 82 wRC+ into today. Yikes.

But his underlying metrics are good. Carpenter owns a 41.7% hard-hit rate and 50.0% fly-ball rate, and both his strikeout rate (23.9%) and walk rate (14.8%) are right in line with his marks from last season (23.3% strikeout rate and 15.1% walk rate).

Carpenter is getting hurt by a .250 BABIP and 7.5% homer-per-fly-ball rate (HR/FB) -- both of which are below his career averages of a .315 BABIP and 11.3% HR/FB.

While there's nothing alarming in his profile, we can't just assume Carpenter is going to go on an otherworldly run like he did last campaign and be one of the game's best two or three hitters for a four-month span. He should produce better than he has been, though. His batted-ball profile and unfavorable luck in BABIP as well as HR/FB rate point to some positive regression, and now is the time to buy Carpenter, especially in OBP formats, where he's particularly valuable.

Jose Ramirez, 3B, Cleveland Indians

Ramirez was a top three pick, on average, this spring, per NFBC average draft position data. He hasn't come close to justifying that draft cost as he's the 33rd-ranked third baseman by ESPN's Player Rater.

There's a chance he's just not fully healthy. He had to be carted off the field late in spring training after fouling a ball off his leg. He ended up being able to play on Opening Day roughly a week later and hasn't gone on the shelf, but maybe he's not right. If so, that dings this buy recommendation, but there's been no reports of an injury and we have to assume he's OK if the Indians are willing to keep running him out there every single day.

It's not like J-Ram has been terrible. After all, he just put together a 20-game on-base streak.

The issue has been a total lack of power. He's sporting a .100 ISO, 57 wRC+ and .262 wOBA a season after he amassed a .282 ISO, 146 wRC+ and .391 wOBA.

Now here's the crazy part -- Ramirez's batted-ball numbers are better this year than they were in 2018. He boasts a 39.7% hard-hit rate and 47.2% fly-ball rate through 172 plate appearances in 2019, compared to his 36.1% hard-hit rate and 45.9% fly-ball rate from last campaign.

A .211 BABIP and 5.1% HR/FB rate are the main culprits. The difference between his wOBA (.262) and expected wOBA (.329) is the 12th-biggest gap among all hitters, per Baseball Savant.

He's swiped 10 bags, so he's still contributing in that category, and the power numbers are bound to rise if he keeps mashing hard-hit fly-balls. J-Ram is one of the best all-around fantasy assets out there, and you might be able to get him at a discount.

Nick Castellanos, OF, Detroit Tigers

Castellanos has been a batted-ball deity since the start of the 2017 season, and his numbers this year make up arguably the most mouth-watering profile he's ever had. And despite that, he's got just three home runs in 161 plate appearances, and his .330 wOBA is his worst clip since 2015.

So what's going on?

Oh, it's his HR/FB rate.

In spite of a nice hard-hit rate and a career-best fly-ball rate, Castellanos' HR/FB rate is worse than half of what it's been the last two seasons. His walk rate, strikeout rate, BABIP and ground-ball rate are all right around his usual averages.

Castellanos has an expected wOBA of .355, according to Baseball Savant, and our models project him for 18 taters and a .285 average the rest of the way, which is similar to what Steamer has him for (.272 average and 17 homers).

Playing in a weak lineup in a pitcher-friendly park, Castellanos isn't a super sexy trade acquisition, but he's a solid player who is probably cheaper than he should be.

Nomar Mazara, OF, Texas Rangers

Mazara has exactly 20 homers in each of the last three seasons, and as a 24-year-old with plenty of big-league experience under his belt, it's easy to dream on a big 30-homer season from him at some point.

While his surface numbers -- .302 wOBA, .227 average and six jacks in 143 plate appearances -- say he's taken a step backwards so far this season, there's a lot to like here.

Mazara has mashed his way to a 45.7% hard-hit rate, miles better than his 37.5% mark from 2018, which was a career-best clip. He's also lowered his strikeout rate to 18.2%, a career low. The lack of bottom-line production is twofold: he's got a .240 wOBA, way south of his .290 career average, and his fly-ball rate -- something he's always struggled with -- is a lowly 30.2%.

He'll need up lift said fly-ball rate if he wants to hit more bombs; there's no way around that. But as is, he's been pretty unlucky this season as his expected wOBA of .361, per Baseball Savant, gives him the 25th-biggest discrepancy in wOBA and expected wOBA.

Steamer pegs him to crush 20 more homers, which would get him to 26 for the season, so while 2019 doesn't look like it'll be that huge step forward into 30-home run territory, he's due for some positive regression and is in line for another quality campaign.

Joey Votto, 1B, Cincinnati Reds

One of the best hitters of the last decade, Votto is another guy who, like Ramirez, has seen a huge drop in power. Votto owners have even more reason to be worried, though, since he popped just 12 jacks last year, which makes it look like the 35-year-old first baseman is succumbing to Father Time.

That doesn't fully explain what's happening.

Even during his 12-dinger season in 2018, Votto was making solid contact, putting up a 41.0% hard-hit rate. He just wasn't hitting the ball in the air often enough (31.1% fly-ball rate). This year, he's still squaring up plenty of pitches (39.2% hard-hit rate), and he's also getting more loft on the ball with a career-high 44.3% fly-ball rate. But a .266 BABIP and 7.0% HR/FB rate are bogging down his power output.

It's not all bad luck, however, as Votto's strikeout rate has skyrocketed up to 24.4% this season -- a career-worst clip and a huge rise from his 16.2% strikeout rate from 2018 (which was markedly worse than his 11.7% mark in 2017).

All in all, there are some worrying signs in Votto's profile, most notably the increase in punchouts, and one of this generation's best hitters is showing real signs of declining from his lofty perch. With that said, he's still walking a ton (13.1% walk rate), and his batted-ball luck should rebound if he keeps making the kind of contact he's been making. Votto can be a nice pickup in fantasy, and with him ranked 47th among first basemen, per ESPN's Player Rater, the price shouldn't be too much.