Is Mike Yastrzemski a Legit MLB Outfielder?

by Phoenix Desertsong, Baseball Fanatic

On September 17th, 2019, Boston Red Sox legend Carl Yastrzemski and his grandson Mike reunited at Fenway Park for the first time in awhile. It’s a dream come true for the 29-year old rookie outfielder for the San Francisco Giants who hails from Andover, MA. After playing four years at Vanderbilt, Mike has spent seven seasons in the minors, all for the Baltimore Orioles system until this year. His ascent to the Major Leagues was years in the making, and now he makes his debut at Fenway in left field, the position his grandfather roamed for many years for the Red Sox.

While it’s highly unlikely that we’re seeing the beginning of a Hall of Fame career for Mike Yastrzemski, his numbers in 2019 are pretty solid. Through 96 games, Mike hit .265/.324/.509 good for a 115 OPS+. Mike Yaz also had 19 home runs and 51 RBI. In his minor league career, he had decent, but sort of average numbers. In fact, the projection systems all saw Mike Yastrzemski as more of a 4th outfielder with some pop.

On that very first game at Fenway Park, Mike Yastrzemski hit his 20th home run of the season. It was a home run broadcast everywhere, a league-wide sensation. "Little Yaz" would finish the 2019 season hitting .272/.334/.518 with 21 HR. With the sudden success of a Hall of Famer's descendant, it's little surprise that Mike Yastrzemski rookie cards have been hot since that special moment at Fenway.

So, why is Mike Yastrzemski so good all of a sudden? Part of his success is fueled by a much better batting line on the road vs home and success against lefties as a left-handed batter. His 2019 season BABIP was .325, which isn’t incredibly high. Outside of a brutal month of June and some back issues, "Little Yaz" has actually been even better than his overall batting line would suggest for most of the season. But, is it sustainable success?


What Does StatCast Say About Mike Yastrzemski?

While Mike Yastrzemski is indeed related to Carl, it’s not fair to compare him to his Hall of Fame grandfather. But because his numbers don’t seem fluky on the surface, we need to look at his actual quality of contact. Right off the bat - pun not intended - StatCast shows us that he may be a bit lucky after all. But, it’s not that drastic. Mike’s expected batting average is .251, which is certainly significantly lower than his actual mark of .272. But, his expected slugging percentage of .484, when you filter out the loss in batting average, isn’t much off his current performance.

While Mike Yastrzemski may not develop into the slugger his grandpa was, StatCast’s expected wOBA of .341 isn’t that far off of his actual .357 wOBA, and still quite above league average. There are a couple of other things in his favor, too. StatCast tells us that Mike has above average sprint speed on the bases and an above-average jump on the ball in the outfield. While he has only stolen two bases, he’s been running the bases well, and he’s been a plus defender in the outfield, mostly in left and right field.

Although he’s hit some weak balls, he’s been barreling the ball well, and his hard hit percentage is in the 74th percentile. Having above average power and a respectable on-base percentage while adding above average baserunning and fielding to the mix is a decent package. Right now, Mike Yaz really looks like a league-average corner outfielder. He’s not blowing anyone anyway, but he was a really nice pickup for the Giants.

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Why Did the Orioles Give Up on Mike Yastrzemski?

I’m not so sure that the Orioles expected Mike Yastzemski to become a solid regular all of a sudden. He was invited as a non-roster player in spring training and obviously showed enough to the Giants scouts that they wanted to trade for him. The Giants surrendered starting pitcher Tyler Herb, who would go on to pitch fairly well in AA Bowie for the Orioles before struggling mightily in AAA. It’s clear that the Orioles made a mistake with this deal.

Credit goes to the Giants scouting in clearly selecting a player who was ready to breakout. Soon as he went to AAA for the Giants, he tore the Pacific Coast League to pieces. Even though it’s an offense-friendly league, his .316/.414/.676 slash line with 12 HR in 40 games was obviously impressive. With the Giants outfield situation a mess for most of the year, Mike Yaz has found a home in left field alongside brilliant defensive outfielder Kevin Pillar. 

It’s safe to say the Orioles regret making that trade, because it’s very possible that Yaz would be roaming Camden Yards with Trey Mancini and Anthony Santander right now. While it’s not clear that Mike Yastrzemski is going to become much more than what he is right now - a very useful player - the Orioles have to be kicking themselves. The Giants are more than happy to have him, as he’s a legitimate MLB starting outfielder.