New Role, New Glory: Former Reliever Strive As…

It is common to see pitchers fail in a starting role and then succeed as a relief pitcher. Whether that is due to not having enough depth in their arsenal or command issues, it happens all the time. Recently, we have seen successful relief pitchers continue their success in a starting role. A great example of this phenomenon, among many others, is San Diego Padres starting pitcher Michael King. King was a valuable relief pitcher for many years for the New York Yankees before becoming a starter in August of the 2023 season. Down the stretch, he was one of the best starters in baseball with a 2.31 ERA and 1.11 WHIP over nine starts.

King possessed many of the ideal characteristics of a quality starting pitcher. He has multiple fastballs, a strong sweeper, and a changeup to use against left-handed hitters to go with quality command. His results in this end-of-season stretch helped him become a major piece in the trade package that sent him to San Diego and Juan Soto to New York. In his first full season as a starter, King excelled.

Michael King Starting to Flourish as Starter for Padres

Arsenal

Michael King’s arsenal consists of a four-seam fastball, sinker, sweeper, slider, and a changeup. This repertoire allows him to have a flexible approach to both lefty and righty hitters. He can use an east-west approach against right-handed hitters with his sinker and whirling sweeper. And versus left-handed hitters, he can use his four-seamer at the top of the zone and throw his changeup low and away off of it. He also commands all of his pitches very well, with four out of his five pitches having an above-average Strike%. Here is how he used his pitch mix against both hands.

His changeup proved to be his best swing-and-miss pitch. It produced a gaudy 24% swinging strike rate against right-handed hitters and 21.5% against left-handed hitters. Furthermore, it was his go-to weapon against lefties and it produced excellent results, allowing a feeble .489 OPS. It was simply one of the best changeups in baseball, tying for fourth among all changeups by Baseball Savant’s run value. In terms of allowing hard contact, his changeup had the lowest xwOBA of any of his pitches against hitters from both sides. King’s changeup was good when used in 2023, but he significantly ticked up the usage in 2024, going from 14.5% to 24.6%.

While his changeup never graded out well by Stuff+, it is important to keep in mind that changeups are the trickiest pitch to fully capture the value of in a stuff model. The success of changeups is predicated on the interaction effect with the primary fastball as well as deception. Ideally, the fastball and changeup create a tunneling effect and look the same out of the hand before the changeup fades away from the hitter.

Workload Concerns

A possible concern for a pitcher transitioning from the bullpen to the rotation is how they will handle a larger workload. The increase in number of pitches thrown, batters faced, and innings pitched all take their toll. For one, it tests them physically, as many pitchers will get injured with the added load. Second, many pitchers’ limitations get magnified as their volume of work increases and they face more batters. Also, they can slow down and see their stuff and velocity wane as the season goes deeper.

When digging into King’s season, there were some possible warning signs early on from a velocity perspective. He started the season averaging 94.22 MPH on his four-seam fastball. He then consistently settled around 93.5 MPH or so on a start-to-start basis. The importance of gaining and losing ticks of velocity is crucial in this age of MLB. King’s start-of-the-season velocity of about 94 MPH is right at the league average for fastball velocity. Maintaining that level of velocity can determine a lot. Roughly two months into the season in late May, King reached his lowest average four-seam velocity of the season at 92.86 MPH, nearly a full tick and a half down from the start of the season. It was a subtle trend at the time, but could have been a development to watch.

After a start on May 27th with his lowest velocity of the season, King slammed the door on any velocity concerns as his workload increased. In 21 starts after that point, King averaged at least 94 MPH on his four-seam in 13 of those starts (61.9%). And also, he never crept below 93 MPH again. His numbers up until that point were not bad with a 4.09 ERA, 1.27 WHIP, and 16% K-BB%. But they were not great either. Here are his numbers following that point in time and corresponding rank among qualified pitchers.

Future Outlook

For a large portion of the season, Michael King was one of the best pitchers in baseball. Additionally, he was the fourth most valuable pitcher by fWAR only behind the two presumptive Cy Young winners Tarik Skubal and Chris Sale, and rookie sensation Paul Skenes. Moreover, King was part of a collection of reliever-turned-starters in 2024 who flourished in their new role. This trend could be something to remember in future years as everyone is yearning for starting pitching.

Michael King proved to be a vital piece of the Padres rotation and a force in the playoffs. He boasts a complimentary arsenal with an elite sweeper and a great feel for locating all of his pitches. With an ace-level season now under his belt, he should be viewed in high regard for the 2025 season and beyond.