The Pitchers with the Best xwFIP: April Edition

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This past offseason, I introduced the pitching metric xwFIP in a series of three posts. xwFIP is an advanced fielding independent pitching metric that not only takes into account walks, hit batsmen, strikeouts, and homeruns, but also the xwOBA on batted balls. The metric takes into account nearly 100% of plate appearances in its calculation. Moreoever, I have showcased that it has greater predictive power than each of ERA, wOBA, FIP, xFIP, xwOBA, and SIERA in predicting future run prevention performance of a pitcher.

This season, I’ll be posting the xwFIP leaderboard each month so we can see the starters and relievers that are most likely to have continued success, along with the pitchers who have been lucky and unlucky so far.

Table 1 lists the leaderboard through April 27th for all pitchers in the table with a minimum 10 innings pitched (IP) so far this season.

Table 1: The 30 pitchers with the best xwFIP through April 27th (minimum 10 IPs).

Oakland A’s flamethrowing closer Mason Miller is the best one-inning pitcher in baseball so far in 2024, with a measly xwFIP of 0.90. Miller’s average fastball velocity of 100.7 mph is the highest in the MLB, and his slider’s elite vertical drop of 5.3 inches more than average, coupled with its sharp horizontal break of 4.2 inches above average, has proven devastating.

Cardinals closer Ryan Helsley, Mets reliever Reed Garrett, Braves reliever Joe Jiminez, and Angels reliever Luis Garcia follow Miller in the top five. Futhermore, the starting pitchers that make the leaderboard of MLB’s elite 30 arms include Sonny Gray, Joe Ryan, Ranger Suarez, Jared Jones, Zack Wheeler, and Tarik Skubal.

Table 2 lists the 30 starters with the best xwFIPs through April 27th, with a minimum of 20 innings pitched so far this season.

Table 2: The 30 starting pitchers with the lowest xwFIP through April 27th (min. 20 IP).

Joining Ryan, Suarez, Jones, Wheeler, and Skubal - Garret Crochet, Corbin Burnes, Tyler Glasnow, Ronel Blanco, and Yusei Kikuchi round out the top ten starters who have at least 20 innings pitched.

Yoshinobu Yamamoto ranks 27th among starters with a 3.64 xwFIP, which indicates worse performance than his ERA of 3.54 and his FIP of 2.76. This is due to the hard contact Yamamoto has surrendered thus far in the season.

The Braves’ lefty Chris Sale is enjoying a resurgent season after years of injury and his subsequent trade from Boston, ranking 30th among starters with a 3.72 xwFIP.

Table 3 lists the 30 pitchers most likely to regress in run prevention for 2024 (minimum 10 IP).

Table 3: The 30 pitchers most likely to regress in run prevention in 2024 (min. 10 IP).

Matt Strahm, Simeon Woods Richardson, Jordan Leasure, Tim Herrin, and James McArthur are five of the pitchers who have pitched into the best luck so far in 2024. Shota Imanaga has outperformed his countryman Yamamoto in ERA and FIP, but trails him in xwFIP.

Lastly, Table 4 lists the 30 pitchers most likely to improve in run prevention in 2024.

Table 4: The 30 pitchers most likely to improve run prevention in 2024 (min. 10 IP).

April’s most-likely-to-improve list has Dominic Leone, Adbert Alzolay, Chris Devenski, Kenta Maeda, and Zack Thompson at the top.

Michael Kopech is one pitcher with an elite xwFIP of 2.64 that has yet to see results on the field with an ERA of 4.38 and a FIP of 5.04. Based on this analysis, I expect Kopech to turn it around.