Using Pete Alonso to illustrate 'x' stats

Baseball imitates life and if there’s one thing we know about life, it’s that it’s not always fair. And nowhere was that more evident than in the final out of Wednesday’s game. Pete Alonso did everything right. He crushed a pitch, with a launch angle and exit value that results in a hit 99 times out of 100. Except the end result was the one time out of a 100 that a ball hit like this winds up an out, thanks to a great play by the opposing team’s center fielder.

In this case, Alonso’s AVG on this ball is .000 but the same ball had a .990 xBA. What is xBA? The Statcast glossary defines it thusly, “xBA measures the likelihood that a batted ball will become a hit. Each batted ball is assigned an xBA based on how often comparable balls -- in terms of exit velocity, launch angle and, on certain types of batted balls, Sprint Speed -- have become hits since Statcast was implemented Major League-wide in 2015.”

Sprint speed didn’t factor into this ball hit by Alonso, which had a 108.7 exit velocity and a 25 degree launch angle. Obviously, this was an extreme case. Still, we can and do see plenty of times where there’s a smaller yet still noticeable difference between reality and what’s expected. And over a larger sample than one plate appearance, we can see it a player – or team – is hitting into good or bad luck.

Here’s how the batters for the 2025 Mets have fared in this regard:

Of the 13 hitters for the Mets this year, two have been fortunate with their batted balls – Starling Marte and Jesse Winker – and two have pretty much the results they should have – Luisangel Acuna and Juan Soto. But MLB as a whole so far has a 27-point difference between xSLG and actual SLG, making Brett Baty and Hayden Senger league-average in this respect. So, let’s look at the remaining seven hitters and how far below their xSLG they are:

65 points – Pete Alonso
88 points – Brandon Nimmo
95 points – Francisco Lindor
132 points – Luis Torrens
177 points – Tyrone Taylor
182 points – Jose Siri
204 points – Mark Vientos

It’s interesting how the two DHs have been fortunate, while the two CF have not.. And as productive as Torrens has been at the plate, he’s making even better contact.

Eight days ago in the Open Thread, it was noted how Alonso had a .353 SLG but a .615 xSLG. In the interim, his actual SLG moved heavily towards his xSLG, even with his xSLG increasing. Today, those numbers are .692 and .757, respectively.

How has he managed this? Early in the year, Alonso was hitting the ball hard but with too many grounders. After five games, Alonso had a 53.3 GB%. And now he has a 37.8 GB%. In the past eight days, he’s continued to hit the ball very hard, just mostly in the air, rather than into the ground. How hard has Alonso been hitting in this stretch? He has a 54.5% HrdHit% and a 45.5 Med%. Not one of the 25 balls he’s hit fair has been a soft-hit ball.

While Alonso had the biggest discrepancy between his contact and results in terms of SLG, now it’s Vientos. But while we were able to identify why Alonso was having poor results – too many grounders – it’s not so easy with Vientos. With a 25.0 HrdHit%, he’s not making a lot of hard contact. But it’s mostly medium contact, as he has a 62.5 Med% - so it’s not like he’s making weak contact. And a .188 BABIP certainly isn’t helping matters.

If we’re fortunate, 10 days from now Vientos will make the step forward in results that Alonso did. But there are other deserving candidates besides Vientos.

When we look at this on a team basis, the Mets are below league average in AVG, SLG and wOBA, which matches our disappointment with the offense so far. Yet, they are above league average in xAVG, xSLG and xwOBA, with a 70-point deficit in SLG between actual and expected. As a team, the quality of contact the Mets are making trails the actual results by a significant margin.

Then again, no one ever said life was fair.