Is It Legit?: Willi Castro and Zach McKinstry

Is it simply a hot stretch or is there something more going on?

Believe it or not, we’re already 10 weeks into the fantasy baseball season! For those of you in head-to-head leagues, you’re likely about halfway through your regular season schedule, and at this point, the strengths and weaknesses of your fantasy squads should be pretty apparent.

Now that we’re in the heart of the season, most players that have started hot and stayed hot have proven that what they’re doing is legitimate, so today we’re shifting focus a bit. Instead of analyzing players that have impressive season-long stat lines, we’re looking at a group of guys that have been on an absolute tear recently and trying to determine if their newfound success is here to stay or just a flash in the pan.


Willi Castro, OF/3B, Minnesota Twins


Since Willi Castro became a full-time starter for the Twins back on May 16th, he’s been one of the best fantasy producers in the game. In his 67 plate appearances over that period, Castro is slashing .323/.348/.548 with four home runs and nine stolen bases. He’s been a great waiver add in deep leagues and has even started drawing notice in shallower leagues as his Yahoo! roster rate is now up to 50%.

We’ve seen him show flashes of this kind of play before, particularly in the abbreviated 2020 campaign. In 36 games, Castro hit .349/.381/.550 and finished that short season with a 154 wRC+. Since then, it’s been pretty much all downhill. He struggled mightily during his final two years in Detroit, but has looked rejuvenated with his new club in Minnesota.

You can see that Castro’s 2020 breakout is certainly the outlier here, especially with that unrepeatable .448 BABIP, but is the rest of what he’s doing sustainable?

On the plus side, Castro’s increased his barrel rate significantly. It’s at 11.4% for the season, over three times higher than it was last year and more than double what it was in 2021. Castro isn’t just hitting the ball harder, though, he’s also hitting it at ideal launch angles more often. His Sweet Spot% — a stat that measures balls hit with a launch angle between 8 and 32 degrees — is up to a career-high 46.8%. Castro is also pulling the ball more than ever, allowing him to drive the ball more often. When you put all of those things together, you get good batted-ball results, and that’s exactly what Castro is experiencing the last few weeks.

Now for the negatives. There’s a pretty glaring issue in that table above: his strikeout rate is soaring. After two straight years of reining in his punch outs, he’s striking out at a career-high rate. All of his strikeout, walk, whiff, and chase rates are in the 11th percentile of batters or worse. Another downside to Castro is that he’s on a very crowded Twins’ roster. His ability to play nearly every position certainly helps, but if the injury-prone team ever gets fully healthy I think Castro’s role is more super utility guy who starts three days a week than it is everyday starter.

Verdict: Pretty legit. It’s hard to ignore that Castro is barreling the ball more often, hitting it at an ideal launch angle more frequently, and pulling his hits more than ever. That’s a recipe for success at the plate if I’ve ever seen one. That doesn’t mean Castro is a must-add in all league types, though. He’s certainly worth a look in 12-team and deeper leagues, but you may want to shy away in points and OBP formats with the ugly strikeout numbers. The potential for him to lose playing time scares me, but for the time being I’m taking a chance on Castro in deep formats and hoping he keeps cracking the lineup most days.


Zach McKinstry, 2B/3B/OF, Detroit Tigers


Taking over Castro’s utility role in Detroit this year is Zach McKinstry. The Tigers traded for him just before Opening Day, landing him in a deal with the Cubs on March 27th. McKinstry opened the season as the utility guy, starting just four of the team’s first 11 games. It didn’t take long for McKinstry to impress his new club, though. Starting on April 26th, McKinstry took over the team’s leadoff spot when facing a righty, and he hasn’t looked back.

Since April 26th, McKinstry has been the 18th best position player in the sport according to his 1.3 fWAR. Even more impressively, his .413 OBP is the fourth-best mark in the majors over that same stretch, and his 138 wRC+ is 29th best.

McKinstry’s never enjoyed this kind of success in his big league career before, but he’s never really had much of a chance. He came up through the minor leagues in an absolutely stacked Dodgers’ farm system and understandably struggled to hang on to a spot on the big-league roster. He had a decent run of 171 plate appearances in Chicago last year, but his 78 wRC+ wasn’t enough for the team to want to give him another opportunity.

Let’s take a look at some of his peripheral numbers from the last few years and see if we can spot any differences.

Wow! Pretty much everything is better across the board.

The dramatically improved results at the plate may be the results of an approach change with his new team. According to Chicago White Sox broadcaster, Steve Stone, McKinstry shared that the Cubs wanted him to pull the ball and try to muscle it out of the park, but the Tigers are letting him spray it all over. We don’t know if that’s exactly what’s caused the breakout at the dish, but some numbers support it. McKinstry’s pull rate is down to a career-low 37.2%, and he’s hitting the ball to centerfield more than ever at a 39.8% clip.

McKinstry’s game was never going to be his power production, but it’s impressive just how quickly he’s turned around his plate discipline numbers. Getting on base, whether via a walk or slapping the ball to all fields, is probably his best bet to be an above-average offensive player with the speed he carries. McKinstry has already swiped 10 bags this year, and although his sprint speed has always been impressive, it’s never resulted in eye-popping stolen base totals. Even as he worked his way through the minor leagues, the most stolen bases he ever had in any single stint was eight during his 384 plate appearances with the Dodgers’ Double-A squad back in 2019. Stolen bases are largely a factor of opportunity and willingness to run, and it looks like McKinstry has the green light. He’s only been caught once in his 11 attempts, so I don’t think the Tigers will have him slow down anytime soon.

Verdict: Legit. McKinstry looks like one of the season’s more surprising breakout players, and the numbers behind the results all point to him being legit. Each of his xWOBA, xBA, and BB% are all in the 90th percentile of hitters or better, and his xSLG, Barrel%, and Whiff% are all 75th percentile or better. He’s not going to make much of a difference for your fantasy team’s power output, but he’s shaping up to be a good batting average, run, and stolen base producer, and if you’re in a points or OBP league, he’ll be even better. If you want an even deeper dive into McKinstry and the changes he’s made this year, check out our very own Ben Pernick’s fabulous piece from a few days ago.


Leody Taveras, OF, Texas Rangers


Still just 24 years old, Leody Taveras is looking like a post-hype breakout candidate. He started the year on the IL and then struggled at the plate after he returned in mid-April, but since the beginning of May, he seems to really have turned a corner. Since May 1st, Taveras is hitting .359/.407/.524 with three home runs, 16 runs, 18 RBI, and two stolen bases.

In his fourth season at the big league level, it looks like Taveras is finally figuring out big-league pitching – both his strikeout and walk rates are career-bests, at 21.4% and 7.5%, respectively. PLV agrees, as his strike zone judgment and his swing decision metrics are both improved over previous years. When he is hitting the ball, he’s making solid enough contact. His .286 xBA is in the 81st percentile of hitters and his hard-hit rate is at a career-best 42.6%. The one major troubling sign for Taveras? In his hot stretch since May 1st, his BABIP is .425. Now, he does always run high BABIPS – he was at .344 over the full season last year – but he won’t maintain one over .400 over the course of the season.

Verdict: Mostly legit. Taveras has tangibly improved his plate discipline ability which should go a long way in making him more fantasy relevant. However, he doesn’t tap into his power much, which means he’ll be largely dependent on whether his batted balls are falling for hits. They are right now, but that can change quickly. I’m interested enough in Taveras that I’d look to add him in 12-team and deeper leagues if you need some batting average or stolen base help. It’s great that he’s hitting in one of the game’s best lineups, but he’s stuck in the nine-hole, so his boosts from the hitters around him will be muted more than others in the lineup.


Merrill Kelly, SP, Arizona Diamondbacks


Merrill Kelly is putting together another strong season for the Diamondbacks, but he’s been particularly impressive over his last seven starts. Since April 28th, Kelly is 6-0 with a 2.44 ERA, 0.92 WHIP, 30.4% strikeout rate, and a 6.4% walk rate. Both his season-long swinging strike and chase rates are at career highs and as a soft-tossing 34-year-old that’s not what you’d expect.

Digging into the underlying data, Kelly’s arsenal looks nearly identical to last year’s. His pitch mix hasn’t changed much, his velocity has ticked up just a hair, his spin rates are up a tad too, and the break on his pitches is almost unchanged. There’s no obvious thing that he’s doing so much better that we can point to as the reason his strikeouts are soaring. Kelly is running a .248 BABIP which is over 30 points below his career average, so that’ll likely regress, but it’s important to note that the Diamondbacks’ defense ranks second in Outs Above Average. That BABIP could very well stay lower than we expect with a solid fielding group playing behind him.

Verdict: Not Legit. There’s no clear reason that Kelly should be striking out as many batters as he is right now. It’s hard to quantify pitch sequencing and tunneling in available data, so I wonder if he’s just doing an excellent job in those two departments and that’s what’s gotten him on such a great run recently. If you roster Kelly and want to sell high on him, I don’t blame you, but he should stay good enough that’ll be worth a roster spot all year, so there’s no need to move him if you want to see how long you can ride out this hot streak.


Michael Massey, 2B, Kansas City Royals


As he’s approaching 400 career plate appearances, it looks like Michael Massey is starting to feel comfortable against MLB pitchers. The Royals’ 25-year-old second basemen started the year awfully slow, slashing .167/.173/.179 in March and April, good for -14 wRC+. Yes. That’s a negative wRC+, meaning he was 114% worse at producing runs than the average hitter over the season’s first month. Massey has turned things around quite a bit since then, though, as his slash line stands at .304/.391/.494 and a 145 wRC+ since the beginning of May.

Massey’s dramatic improvement is largely due to much better plate discipline. He cut his strikeout rate from 38.3% to 23.9% and improved his walk rate from 1.2% to 9.8%. He’s also doubled his barrel rate while increasing both of his flyball and pull rates, leading to many more extra-base hits.

Verdict: Somewhat legit. We’ve seen significant improvement in Massey’s profile from March/April to May, but given that he’s still in the early stages of his career and didn’t carry much prospect pedigree, I’m not ready to declare this a fully legitimate stretch. We are working with small sample sizes when we break things down into stretches that are just a few weeks long after all. Massey is absolutely worth an add in 15-team leagues, and maybe even 12-team leagues depending on your team’s needs, but with a .370 BABIP since May 1st and a light-hitting profile, things could swing quickly for him if he has a week or two when his hits aren’t falling.

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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