For one reason or another, minor league starters sometimes turn into relievers upon arriving in the majors. Elite pitchers who will struggle as major league starters, whether due to command struggles or a lack of deep repertoire, can reinvent themselves as high-leverage relievers. But what about the opposite? Can relievers transition to starters effectively? Three former relievers are all trying to make this transition today.
Michael King, San Diego Padres
Statistics until May 6. 42.0 IP, 4.96 pCRA, 24.8% K%, 12.4% BB%, 10.0% Barrel%, 41.7% GB%, 31.1% CSW%, 11.1% SwStr%, 26.4% Whiff/Swing%
Michael King started six games for the Yankees last season, and he was so effective that the Padres made him a key role in the return of Juan Soto. However, King has had a rough start to the season. He is in the 23rd percentile in walk rate, 20th percentile in barrel rate and 56th percentile in strikeout rate. His struggles ultimately come down to the imperative, especially for his four-seamer and sinker. As you can see from the heatmaps, King leaves both pitches right in the middle of the zone, resulting in barrel rates of 14.7% and 22.2%, respectively. Looking back from his start with the Yankees, both pitches have regressed from a material standpoint; they each lost 1.7 mph, the quarterback lost 0.9 inches of vertical break, and the sinker lost 1.7 inches. run on hand. Given that none of the infield had elite movement or speed to begin with, this regression is concerning.
However, there are still effective pitcher pieces; his primary off-speed pitches, the changeup and sweeper, are still elite pitches. King uses both to limit hard contact, as no pitch has yet given up off the barrel, and produces a high rate of whiffs at a 41.1% changeup and a 28.8% sweeper. If King is going to be the pitcher the Padres thought they were getting when they gave up one of the best players in baseball, he needs to stop dropping his fastball and diving into the heart of the zone. If he can do that, figures to be a key rotation piece for a Padres team with October aspirations.
Jordan Hicks, San Francisco Giants
Statistics until May 6. 38.0 IP, 4.32 pCRA, 19.7% K%, 8.6% BB%, 6.7% Barrel%, 58.1% GB%, 27.9% CSW%, 9.9% SwStr%, 22.7% Whiff/Swing%
Jordan Hicks was one of the hardest-throwing pitchers with the Cardinals last season, but the Giants signed him to a four-year contract to become the starter. The consensus was that this was risky, especially for a guy with a history of injuries. So far, though, this signing has paid off big, although I don’t think he’s as good as his 2.30 ERA suggests. One repertoire change that has helped Hicks is increasing the use of dividers. He’s using it 23.3% of the time this season, after using it less than 2% of his pitches last season. It’s his primary pitch, as he uses it 37.6% of the time in 2-strike situations, and his primary pitch to generate 43.2 whiffs. Jordan’s splitter tends to be hard hitting, as evidenced by the 11.8 bp.%. Hicks’ other offspeed pitch, the sweeper, is also very effective as it plays well off his submarine and gives him a pitch that moves toward the glove side. It produces whiffs at about average speed, but is elite at minimizing harsh contact, having yet to give up the barrel this season.
Because he is a primary pitcher, he will never be an elite hitter. But if Jordan Hicks can continue to generate ground balls at an elite rate (he’s in the 89th percentile), he could be a great addition to the Giants’ strong rotation behind Logan Webb and Kyle Harrison.
Reynaldo Lopez, Atlanta Braves
Statistics until May 6. 30.0 IP, 3.46 pCRA, 27.0% K%, 8.7% BB%, 5.4% Barrel%, 44.6% GB%, 30.5% CSW%, 14.8 SwStr%, 30.0% Whiff/Swing%
Reynaldo Lopez was actually a starter for the White Sox in 2018-19 before being converted to a reliever, and a pretty good one at that. The Braves signed him this offseason with the goal of making him a starter. So far, it’s paid off, especially given Spencer Strider’s injury. Lopez has been elite in limiting barrels, as he has yet to yield to both his slider and curveball. The slider, which Reinaldo uses 29% of the time, is his best pitch. He’s added depth to it, and the results have been impressive: 39.5 K-BB%, 1.02 pCRA, 0.0 Barrel%, 61.9 GB%, 31.8 CSW%, 23.3 SwStr%, and 46.2 Whiff/Swing%. His fastball has been elite in limiting barrels, as it has a barrel rate of 4.5%, well below the average of 10.1%. However, this could be due to regression, as Lopez’s average exit velocity of 91.1 mph and hard strike rate of 48.8% on his fastball are in line with the pitch average.
Reynaldo Lopez was a shrewd acquisition for a Braves rotation that started the year ravaged by injuries and unexpected struggles. While I doubt Reynaldo Lopez will maintain his 1.53 ERA for the rest of the year, if he can continue to be productive it will go a long way for the Braves to overcome the October demons that have haunted them in recent seasons.
These three pitchers have had varying degrees of success. As the season progresses, it’s fair to expect some regression as they adjust to their increased workload. While King struggled out of the gate, the other two proved that the transition from starter to reliever can be productive, albeit with a limited workload to start the season. With the constant need for starting pitching and the high cost of high-end starters, it should be noted if teams are looking for relievers in an effort to fill out their rotation.
