Is It Legit?: Jonah Heim, Mitch Keller, Eduardo Rodriguez

What can we expect from these five players the rest of the season?

It’s the middle of May, and we’ve got six weeks of the 2023 fantasy baseball season in the books. Team records and player statistics are starting to become a whole lot more concrete as sample sizes continue to rise, giving us more and more data to analyze to determine whether what we’ve seen over the first 40 or so games is legitimate, or just a result of things going a player’s way more often than not.

Today, we’re diving into five hot starters to see if they’ll keep things rolling the rest of the way, or if this is the time to sell high on a performance that will likely come back down to earth soon. Let’s dive in!

Jonah Heim, C, Texas Rangers

The Rangers have the second-highest-scoring offense in baseball, and Jonah Heim is a big reason why. Through 137 plate appearances, the switch-hitting catcher is slashing a remarkable .315/.372/.532 with six home runs, 30 RBI, 25 runs, and has even tacked on a stolen base for good measure. That batting line comes out to an impressive 150 wRC+, the second-highest mark among catchers trailing only Sean Murphy, and the 15th-best among all hitters.

Heim has gotten better and better every year he’s been in the big leagues, and now in his prime at 27 years old, he’s putting up his best season yet. How? By fixing one of his biggest weaknesses — hitting four-seam fastballs. In 2021 and 2022, Heim posted -7 and -5 run values when facing the pitch, and this year he’s totally flipped that script, posting a 4-run value against four-seamers so far.

Here’s a look at how Heim’s performed against most pitchers’ bread-and-butter fastball, including his actual results and Statcast’s quality of contact metrics:

Not only is Heim hitting the four-seamer well, but he’s also improved his batted ball profile as a whole. He entered the year with a career 39.6% groundball rate, and has dropped that number a whole ten percentage points to 29.6%. In turn, he’s hitting many more line drives (25.5% up from 17.7%) and fly balls (44.9% up from 42.7%) as he gets the barrel to the ball more often — his 12.2% barrel rate is nearly double his previous best.

As a switch-hitter, Heim has always performed much better swinging the bat right-handed, and while that’s still the case this year, he tweaked his swing from the left side of the plate and it’s paying dividends. In an article for FanGraphs last week, Esteban Rivera covered a few hitters who added movement to their loads, and Heim was one of the featured players. The change seems to be paying off as Heim has raised his wRC+ as a left-handed hitter from 83 last year to 127 this year.

MLB rule changes have also been a boon for Heim, especially when he’s swinging left-handed. Last year he was shifted 78.2% of the time while batting lefty. Heim posted a .263 wOBA against the shift and a .342 wOBA without it. With teams no longer able to stack three infielders on the right side, Heim is enjoying even more success with a .356 wOBA through 104 lefty plate appearances.

Verdict: Legit. Heim has been getting better and better every year he’s been in the big leagues, and now in his fourth season, we may be seeing what he’s fully capable of bringing to the plate. Difference-making catchers are hard to come by in fantasy, so if you were lucky enough to draft Heim or pick him up from the waiver wire in the season’s first few weeks, enjoy the strong production and hold tightly to one of the game’s best-hitting backstops.

Mitch Keller, SP, Pittsburgh Pirates

The Pirates’ jumping out to one of the best records in baseball was one of the most fun early-season storylines this year, but while that strong showing has quickly faded, Mitch Keller’s great run has not. I mean, just look at this!

Did a single fantasy player think this was going to happen? I’d wager probably not.

Keller has found success by increasing the quality of nearly every single one of his pitches. All of his offerings have ticked up at least slightly according to PLV this year, save for the curveball that is his worst pitch, and has taken a slight step back. It isn’t just PLV that’s taken notice of Keller’s improvements either. Eno Sarris’ Stuff+ metric shows all of his pitches as better this year, except his curveball and changeup.

Not only has Keller made his arsenal perform better this season, but he’s also added a new pitch to his mix: a cutter. PLV sees it as just slightly better than a league-average cutter, but it’s gotten great results. Batters are hitting just .179 against the pitch with a .267 wOBA, although it’s overperformed according to its .320 xWOBA.

Overall, you can really see the growth in Keller by looking at the Quality Pitch percentage (QP%) in his PLV table. League average QP% is 46.3%, but Keller had never even posted a QP% above 40% until this year. His current mark of 52.5% is in the 88th percentile of MLB pitchers.

This early in the season, pitchers can ride out hot stretches when they’ve faced a favorable schedule of weak offenses, but that isn’t driving Keller’s success. He went at least six innings with three or fewer earned runs against the Red Sox, Astros, Cardinals, Dodgers, and Orioles, plus five innings with just one earned run against the otherworldly Rays’ lineup.

Verdict: Legit. We’re certainly not used to seeing Keller perform this well, but pitch-tracking metrics support his breakout. Keller’s been all kinds of impressive through his first nine starts, and his most recent was his best yet. He dominated the Orioles on Sunday, striking out 13 and allowing just four baserunners over seven innings, and that start came after a complete game shutout of the Rockies. It’s been quite a run for Keller to say the least, and while he’s due for some regression, I think he’s worth holding if you’ve got him on your roster. Of course, if you’re offered an opportunity to sell insanely high, do it, but I’m happy to hold and see if he can keep up this breakout campaign.

Eduardo Rodriguez, SP, Detroit Tigers

Joining Keller in our breakdown today is Eduardo Rodriguez, who may be the other most shocking breakout pitching performer. Through his first 51.2 IP, Rodriguez has gone 4-2 with a 1.57 ERA, 0.79 WHIP, and 24.7% strikeout rate. His performance has been right in line with Keller’s, but unlike the Pittsburgh righty, Rodriguez doesn’t have the pitch performance to back it up.

Rodriguez has a 5.07 PLV thus far, which is exactly league average. Breaking it down by pitch types, only one of his offerings grades out as well above average, and that’s his cutter. He throws it 26% of the time and it’s generated a 5.34 PLV, which puts it in the 72nd percentile. Good, but nothing to write home about, especially when the rest of the arsenal looks just about average.

Pitching metrics are still in their infancy — or at least their toddler years — when it comes to baseball statistics, so I like to cross-reference them to see if the different publicly available metrics agree. Again, looking at Eno Sarris’ Stuff+ model, all of Rodriguez’s pitches are below league average, except for his slider, which comes out to 102 on a scale where 100 is average.

Let’s take a look at the positive for the Tigers’ ace for a minute. He’s done a phenomenal job limiting hard contact. His average exit velocity allowed of 85.7 mph is in the 91st percentile of pitchers. Opposing hitters have compiled just a .215 wOBA against Rodriguez, and the xWOBA tells the same story at .254; both of those numbers are in the 90th percentile or better.

We’ve seen Rodriguez perform well before — he produced 3.7 and 3.9 fWAR in 2019 and 2021, respectively, and a lot of his peripheral numbers fall right in line with those strong seasons.

Two things stick out like a sore thumb: BABIP and LOB%, and not just because I color-coded them. Both of those numbers can tell us the “luck” a pitcher has experienced so far, and for Rodriguez, it seems like he’s enjoyed an awful lot of it. His .209 BABIP will come up back near his .302 career mark at some point, and his 90.4% LOB% is the third-highest among starters who’ve tossed at least 20 innings. That won’t continue.

Verdict: Not Legit. Almost everything points to regression for Rodriguez, so if you can sell high on him, I would do it. In his last SP Roundup article, Nick Pollack called Rodriguez a Vargas Rule and I absolutely have to agree. I wouldn’t blame you for wanting to keep riding out this hot streak, but there’s no telling when it’ll end. His next two starts are at home against the Pirates and on the road in Kansas City, so I can easily see him keeping it up through those games.

LaMonte Wade Jr., 1B/OF, San Francisco Giants

Wade broke onto the scene with a 116 wRC+ in 2021, but constant knee issues sidelined him for most of last year. So far this season, Wade looks back to his old self and is healthy at the plate. He’s been one of the best hitters in the sport, slashing .268/.427/.509 with seven home runs, good for a 163 wRC+ which is the sixth-highest in the league.

A new extremely passive approach is paying dividends for Wade. His 35.9% swing rate is one of the lowest in the league, and when you pair that with his 78th percentile contact rate, you get a batter who is striking out the same amount he’s walking — 18.6% of the time. When Wade is hitting the ball, he’s hitting it hard. His 12.6% barrel rate is a new career high as is his max exit velocity of 111.5 mph.

Verdict: Legit. Wade has become the Giants’ leadoff man when they’re facing a right-handed starter, and I’m fully bought into what he’s doing at the dish. Knee problems can flare up, but if he stays on the field, I think he’s in store for a great season. Hitting leadoff will hurt his RBI production for your fantasy squad, but if you’re in a points or OBP league you’ll be extremely happy with his newfound elite plate discipline.

Alex Cobb, SP, San Francisco Giants

Cobb’s been on a roll this year. After back-to-back starts of seven innings and no runs against the Brewers and Diamondbacks, he’s got a sparkling 1.70 ERA. Now, we know his ERA won’t stay that low, but is there something here to suggest he’s turned himself into a top-20 or top-30 starter?

He introduced a new slider that he’s throwing only 7% of the time. It has a great PLV at 5.66, but it’s allowed a .438 wOBA in the 55 times it’s been thrown. Outside of the slider, Cobb hasn’t made any big pitch mix changes, his velocity is up ever so slightly but not enough to make a meaningful difference, and his spin rates are up slightly too, but again, not enough to make an impact.

Verdict: Not Legit. The story here seems to be Cobb’s 89.6% LOB%. That just won’t stick. It pretty much never does. For reference, last year’s LOB% leader was Julio Urías at 86.6%, and only eight starters that qualified for the ERA title finished with a LOB% above 80%. I like rostering Cobb, especially when you only need to rely on him in good matchups, but I’d happily sell high if someone was interested in my league.

Featured image by Doug Carlin (@Bdougals on Twitter)

Mark Steubinger

Mark loves everything talking and writing about baseball - from every fantasy league format you can imagine to the unending greatness of Mike Trout. Mark has a degree in Sports Communication from Bradley University and works in radio production. He lives in central Illinois where his TV is permanently tuned to Chicago Cubs games.

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