Could this stat spell doom for the red-hot Pittsburgh Pirates?

Why xwOBA might be the canary in the coal mine for Pittsburgh's lineup
Pittsburgh Pirates v Washington Nationals
Pittsburgh Pirates v Washington Nationals / Jess Rapfogel/GettyImages

Much has been made of the Pirates’ hot start to the season. Everyone from to The Athletic has highlighted Pittsburgh’s early success. It’s a great time to jump on the Bucs bandwagon… right?

One stat, though, might indicate that the good times will soon come to an end for the Pirates. According to Baseball Savant’s expected weighted on-base average, Pittsburgh has been the beneficiary of a great deal of luck early in the season. 

xwOBA considers the quality of a player’s contact and calculates the likelihood of that contact (or walk, HBP, etc.) leading to getting on base and subsequently producing runs. (Weighted on-base average, in contrast, simply assigns value to the run value of an event.) Elite players who consistently make good contact, like Aaron Judge or Ronald Acuna Jr., boast xwOBAs above .450. Last year, the league average xwOBA was .320.

Five members of the Pirates’ starting lineup have an xwOBA under .320, meaning their at-bats are not generating as many productive outcomes from a run-scoring standpoint as the league-average player in 2023. These low numbers could be the result of numerous factors, including weak contact and high strikeout rates.

Oneil Cruz, who produces some of the loudest contacts across MLB, has the lowest xwOBA (.247) as of Friday afternoon, and a peek at his xwOBACON (a metric that focuses solely on balls put in play) tells the full story. When Cruz makes contact, his xwOBA jumps to .403. What could possibly be holding him back? Clearly, his 40 percent strikeout rate.

Similarly, Andrew McCutchen’s 42.9 percent strikeout rate is bringing down his run-scoring impact, leading to a .275 xwOBA. In fact, the Pirates veteran has only produced seven batted ball events in his 21 plate appearances.

Henry Davis, while not plagued by the strikeout numbers of Cruz or McCutchen, also ranks fairly low on the xwOBA list at .286. His results can be explained by a lack of quality contact. In two-thirds of his batted balls have either been topped or under. Davis, though, is exhibiting better patience at the plate, cutting his strikeout rate by almost four percent and swinging at pitches outside the zone only 16.4 percent of the time compared to 29 percent in 2023. With more in-game at-bats, he should work his timing out and see his xwOBA rise.

Ke’Bryan Hayes and Jared Triolo also find themselves below the average xwOBA threshold, at .312 and .268 respectively. They have been beneficiaries of some good luck. Their wOBA (the actual run-scoring impact of their at-bats) is .355 and .297, meaning their contributions have had a greater run-scoring impact than would be expected based on the quality of their contact. In other words, they’re overperforming.

The first week of 2024 has felt special, surprising, and even shocking to Pirates fans.

And the stats are here to tell you that it should. Despite the team averaging seven runs a game, more than half of Pittsburgh’s lineup has failed to fuel the run-scoring fire. Sooner or later, this lack of production will catch up as the Bucs regress to the mean.