Fernando Tatis Jr. Isn’t San Diego’s Only Budding Star

Earlier this week, Jay Jaffe detailed Fernando Tatis Jr.’s ascent to superstardom. The 21-year-old shortstop is one of the most exciting players in baseball and is among the league leaders in nearly every meaningful offensive and defensive statistic. But he’s not the only player providing elite production from an up-the-middle position for the Padres. If you filter the position player WAR leaderboards to include players 23-years-old and younger, you’ll find one of Tatis’ teammates just a couple of spots behind him: Trent Grisham.

Among players 23-years-old and younger, Grisham is tied with Ronald Acuña Jr. and Juan Soto at 0.6 WAR. He doesn’t have the gaudy slash line Tatis has posted this year, but his overall offensive contribution has been 39% better than league average, just a couple points behind Acuña’s 141 wRC+. In his 51-game debut with the Brewers last year, Grisham posted a 92 wRC+. This improvement of nearly 50 points has been driven by an eight point jump in walk rate and an outburst of power.

Grisham’s plate discipline has always been a strength. While he was a Brewers prospect, he posted an excellent 15.8% walk rate, though that discerning eye didn’t always translate into low strikeout rates. Eric Longenhagen and Kiley McDaniel described his approach like this in his 2019 prospect profile:

The low batting averages he has posted have been due less to his inability to put the bat on the ball and more to an approach that is passive in excess. Grisham watches a lot of driveable pitches go by. That approach is also part of why he’s never run a season walk rate beneath 14%, and Grisham’s ability to reach base is part of why he’s still such an interesting prospect.

In 2019, it seemed like he had gotten his plate approach figured out, posting a 16.3% strikeout rate between Double-A and Triple-A. But the strikeouts returned in force after he was called up to the majors in August, jumping up to 26.2%, and his walk rate dropped to 10.9%. That elevated strikeout rate has followed him to San Diego but his walk rate has bounced back to 17.9%.

Grisham’s approach with the Padres isn’t marked by excessive passivity however. He’s made strides to use his elite plate discipline skills to swing at the pitches he’s supposed to while not watching too many hittable pitches go by. He’s lowered his swing rate on pitches out of the zone from an already good 22.0% to an elite 17.6%, the ninth best O-Swing rate in baseball. As for swinging at hittable pitches, he’s made some great strides in that area as well, particularly with two strikes. Here’s a look at his two-strike swing rates over the last two years in each of the four Statcast attack zones:

When his back is against the wall, he’s increased his swing rate by 10 points on pitches thrown over the heart of the plate. As a result, his rate of called strikeouts has fallen from 52.1% to 31.8% (the league-average called strikeout rate was 22.6% last year). He’s no longer passively watching hittable pitches go by for strike three.

Grisham’s elite plate discipline has also helped him tap into his raw power. Early in his pro career, he had struggled to translate that raw power to game situations because of his approach. But while he was still in the Brewers organization last year, something clicked and he posted the highest isolated power of his career, peaking with a .396 ISO in 34 games in Triple-A. The key to his power was simply pulling the ball in the air. He dramatically increased his pull rate in 2019 before reaching the majors, but it dropped to just 37.8% after he was called up. This year, he’s pulling more than half of the balls he puts in play and that’s resulted in a 70 point increase in his ISO.

In addition to pulling his batted balls more often, he’s also barreling up the ball far more often, too. He’s increased his barrel rate to 15.2%, which sits in the 90th percentile of all qualified batters this year. His average exit velocity is two miles per hour higher and his maximum exit velocity has reached 111.9 mph this year. All four of his 2020 home runs have been no doubters — they would have gone out in all 30 stadiums. His ability to get on base with his elite plate discipline already made him a valuable offensive contributor. But adding plus power to that package gives him a much higher ceiling at the plate.

Not only is he performing well offensively, Grisham has been one of the best defensive center fielders in the game this year. In Milwaukee, he was shunted to the outfield corners because Lorenzo Cain had center field locked down. Besides his infamous error in the NL Wild Card game against the Nationals, he was solid defensively last year, posting a combined 8.9 UZR/150 and 5 outs above average across all three outfield positions. He’s shown off those excellent skills in San Diego, regularly patrolling center field. He’s already 2 outs above average this year — a mark in the 96th percentile of all fielders — and he’s already made two 5-star catches.

It’s a little early to start taking defensive metrics seriously but his Statcast fielding components paint a promising picture. His outfielder jump is in the 92nd percentile for all outfielders; at its foundation is in an elite reaction time, the highest in the majors this year. That quick first step combined with his elite sprint speed gives him plenty of range to cover center field.

Between his plate discipline, newfound power, defensive range, and speed, Grisham has all of the top-line tools to continue his breakout season. He may not be as well known as Tatis, Acuña, or Soto, but he should quickly prove that he belongs in the conversation as one of baseball’s brightest young stars.