How good was Arizona Diamondbacks rookie Drey Jameson’s MLB debut?

Drey Jameson’s MLB debut for the Arizona Diamondbacks was stellar. He allowed just two hits and struck out five over seven scoreless against a star-studded San Diego Padres lineup.

Whether you use the eye test or read the box score, the right-hander was brilliant on Thursday, helping the D-backs improve to 68-75 in 2022.

In his stellar outing, Jameson joined fellow right-hander Ryne Nelson in an MLB debut yielding seven shutout frames against the Padres this season.

However, beyond the box score, how does Jameson’s first big-league outing measure up against the rest of the league?

Command

Jameson generated a lot of called strikes in his debut. In 90 pitches, 21.1% of them landed for a called strike. By comparison, the only qualified starter — at least one inning per team’s game total — with a higher called strike rate is Adam Wainwright at 21.4%.

“He stood on the mound with poise; commanded his pitches,” D-backs manager Torey Lovullo said postgame.

That he did. While he only generated eight swings and misses, four resulted in strike three.

On top of that, two of the strikeouts came after the Padres got two baserunners on against him with one out in the second inning.

He also struck out Juan Soto twice, once looking — for his first MLB strikeout — and once swinging.

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— Jake Anderson (@jwa1994) September 16, 2022

Batted ball data

Jameson got 21 outs in his MLB debut, and only five came via strikeout. What happened the rest of the time?

There were 18 batted ball events against the 25-year-old on Thursday: 16 for outs, two for hits. Of the the 18 batted balls, 11 were ground balls. The 11 grounders yielded 10 outs, while the other was a sharp single by Brandon Drury, who had the only two hits off Jameson.

That’s a ground ball rate of 61.1%. Only one qualified starter (one inning per team’s game total) achieves a ground ball at a higher rate — Framber Valdez at 66.3%. Valdez is also the only qualified starter with a ground ball rate higher than 57.3%.

“When I did fall (behind in the count), I relied on the sinker to get a ground ball or soft contact,” Jameson said postgame.

Padres hitters had an average exit velocity of 86.7 mph against Jameson’s sinker. Of 365 pitchers with at least 89 batted ball events, that’s in the top 50. Moreover, only two balls were put in play on his changeup and slider combined, and they went for 59.5 and 57.2 mph, respectively.

While his four-seam fastball got hit hard, four of the nine put in play were grounders. Even though the D-backs would probably like the average exit velocity below 97.1 mph, batters hit just .240 with a .263 slugging percentage on ground balls on the season. Even if it’s hit solidly, a grounder is usually an out or a single.

Opposing batters had a launch angle of -2.1 degrees against Jameson. Only three pitchers with a minimum of 89 batted ball events have a lower launch angle against.