Which Relievers Are Stretching Out as Starters This Spring?

The 2024 MLB season was a great year for pitchers who made the move from the bullpen to the starting rotation.

The headliners of the reliever-to-starter class were Garrett Crochet and Reynaldo López. Crochet had never started a game before in his MLB career. López hadn’t gone more than two innings in an outing since 2021. Both were All-Stars last summer and All-MLB finalists last fall.

Angels righty José Soriano was a less-heralded arm who made the switch. After coming out of the bullpen for the first 40 games of his young career, Soriano made 20 starts in 2024, pitching to a 3.36 ERA and 2.0 FanGraphs WAR.

Andre Pallante of the Cardinals was another hurler who took on a primary starting role for the first time. In 20 starts last year, he put up a 3.56 ERA and 1.9 fWAR. Since his rookie season, he has a 3.69 ERA and 2.4 fWAR in 30 starts, compared to a 3.90 ERA and -0.1 fWAR in 108 games out of the bullpen.

Jordan Hicks faded down the stretch in his first year as a starter and had to return to the bullpen. Still, his 4.01 ERA and 4.31 FIP in 20 starts were impressive for a pitcher who had previously only pitched into the fourth inning five times in his career.

Then there was Sean Manaea, who returned to a full-time starting job after filling a swingman role with the Giants in 2023. The southpaw didn’t show any signs of rust from the transition. In fact, he enjoyed what was arguably the best season of his nine-year career, leading the Mets to the NL Championship Series in the process.

Finally, it’s worth mentioning Michael King. The right-hander converted to a starting role with the Yankees down the stretch in 2023, but his 2024 season with the Padres was his first full year in the rotation. He ended up earning down-ballot Cy Young votes thanks to his 201 strikeouts and 2.95 ERA.

So, who could be the next bullpen-to-rotation success story?

Clay Holmes Has the Stuff To Shine

The most obvious candidate is All-Star closer Clay Holmes. The righty signed a three-year, $38 million deal with the Mets to join their rotation. He hasn’t started in the majors since his debut season with the Pirates in 2018.

In his first outing of the spring, Holmes faced the minimum over three sharp innings. He struck out three while generating four grounders and two weak fly balls. His velocity was down, as to be expected, but his arsenal looked deep and effective.

As Jack McMullen said on the Just Baseball Show, “The stuff looked awesome. It’s really only a question of workload.”

Indeed, those are the two big questions facing every reliever-to-starter convert:

Does he have the stuff to survive the move?
And does have the durability to survive the move?

Jeff Hoffman Will Stay in the ‘Pen

Notably, another All-Star reliever on this winter’s free agent market, Jeff Hoffman, will remain in the bullpen with his new club.

Rumor had it that some teams pursued Hoffman as a starter this offseason, but he ultimately signed with the Blue Jays to anchor the back end of their bullpen.

There is no doubt that Hoffman has phenomenal stuff. Moreover, his arsenal is surely diverse enough for him to make it as a starting pitcher. However, he has dealt with numerous injury issues throughout his career, and multiple teams reportedly backed away from him this winter after concerns came up in his physicals.

In other words, Hoffman has the stuff, but he might not be able to handle a starter’s workload.

More Reliever-to-Starter Converts To Watch

More arms who will try to bring the stuff and handle the workload this spring include Caleb Ferguson, Carmen Mlodzinski, Stephen Kolek, Michael Soroka, and Kris Bubic.

Caleb Ferguson, PIT

The Pirates are stretching Ferguson out as a starter this spring to see if he has what it takes to join their rotation.

The lefty has pitched almost exclusively out of the bullpen throughout his six-year MLB career. He has been quite effective in that role, too, pitching to a 3.68 ERA and 3.77 FIP. However, he hasn’t thrown more than two innings in an outing since April 2019.

Ferguson didn’t start in his first spring game for the Pirates, but he did throw two scoreless innings, giving up no hits and just one walk. He certainly seems to be in the conversation for the fifth starter job, although he is more likely to fill a swingman role.

Carmen Mlodzinski, PIT

Another Pirate, Mlodzinski took the ball for the first two innings of Pittsburgh’s Grapefruit League opener. He faced 10 batters, giving up four hits and two earned runs.

The 26-year-old has not started regularly since his 2022 season at Double-A. However, he has been quite successful for the Pirates out of the ‘pen over the last two years, pitching to a 2.91 ERA and 3.64 FIP through 86.2 MLB innings.

Mlodzinski is probably quite far down Pittsburgh’s SP depth chart, behind names like Bailey Falter, Johan Oviedo, and Ferguson, but a strong spring could leapfrog him into the conversation for the fifth starter job.

Stephen Kolek, SDP

The Padres are giving Kolek a chance to start this spring. Like Mlodzinski, he was a full-time starter at Double-A in 2022. However, he converted to a bullpen role in the minors in 2023, and all 42 of his MLB appearances last year came out of the ‘pen.

The righty faced eight batters over two scoreless frames in his first start of the spring. He gave up a pair of hits and struck out two.

All five spots in San Diego’s Opening Day rotation are spoken for, but it will only take one injury (or a poor performance from question mark Kyle Hart) for things to break wide open. Randy Vásquez and Matt Waldron are next up on the depth chart, but each had his struggles last season.

If Kolek stands out this spring, the Padres will almost certainly have starts to give him in 2025.

Michael Soroka, WSN & Kris Bubic, KCR

I left Soroka and Bubic for last (and lumped them together) because they’re in a different category than the other pitchers I named.

Soroka and Bubic are all but guaranteed to start in 2025. Soroka signed with the Nationals to be a starting pitcher, while Bubic is the leading candidate to win the Royals’ fifth starter job out of camp.

What’s more, neither Soroka nor Bubic ever really took on a full-fledged bullpen role.

Soroka made 29 starts in 2019, earning an All-Star selection and finishing second in NL Rookie of the Year balloting. However, he has been plagued by injuries ever since.

He moved into a long relief role this past May – and pitched quite well (2.75 ERA in 36 IP) – but he’ll return to the rotation this year and look to make more than nine starts for the first time since his rookie campaign.

Bubic is another name who has missed significant time with injury. Upon his return from Tommy John surgery this past summer, he pitched out of the Royals bullpen, posting a 2.67 ERA in 30.1 IP. However, the team is planning to reintegrate him into the rotation in 2025.

Thus, Soroka and Bubic won’t be “converted relievers” in the same way the others would be. Still, it will be interesting to see how they perform as they return to the rotation.

Anyone Else To Watch?

With spring training in full swing across Florida and Arizona, it’s a great time to dream about what adjustments your favorite teams’ pitchers could make this season. Transitioning from a bullpen role to the starting rotation is one of the most fascinating changes a pitcher can make.

Is there anyone else to watch in that respect? Maybe. Just Baseball researcher Chap Cunningham dug into the data for us to try to figure out what made so many of last year’s reliever-to-starter converts so successful.

Three names who stood out most from his research were right-handers James McArthur (KCR), Bryan Hoeing (SDP), and Kyle Nicolas (PIT).

McArthur, 28, ranked 12th among qualified AL relievers in called strike plus whiff rate last season. Meanwhile, only two qualified AL relievers outperformed him in both walk rate and groundball rate. Those are good signs he has the efficiency to be an effective starting pitcher.

Hoeing, 28, also throws a ton of strikes and does a good job inducing groundballs. The righty turned his splitter into a key part of his arsenal last year, and it graded out as a plus pitch according to both PitchingBot and Pitching+. In theory, a splitter should help him improve his platoon splits, which would give him a much better chance of sticking as a starter.

Nicolas, 26, throws a 97.4 mph fastball and a pair of nasty breakers. However, to call his control poor would be an understatement.

If Nicolas can rein in the walks, he has the stuff to succeed as a starter. That’s much easier said than done, of course, but it’s not impossible; lowering his walk rate is precisely how José Soriano, a fellow hard-throwing righty, was able to stick in a starting role.

There is no reason – at least not yet – to believe any of these three will be stretching out this spring. On the contrary, all three could be taking things slow due to various injury issues.

McArthur underwent minor elbow surgery this offseason, while Hoeing is currently dealing with some shoulder soreness. Nicolas missed the final two weeks of 2024 with a side injury, though he appears to be back at full strength.

With that said, the Royals, Padres, and Pirates could all use extra starting depth. Indeed, all three of those teams came up earlier in this article. So, keep the names McArthur, Hoeing, and Nicolas in mind, and make sure to give Chap his credit if any of them become starters in the future.

Reliever-to-Starter Converts: Final Thoughts

Starting isn’t easy. There’s a reason so many promising starting pitching prospects end up transitioning to bullpen roles.

Converting back into a starter is even harder. Starting and relieving are two very different jobs that require completely different preparation. There’s a reason so few pitchers can successfully return to the rotation after years in the bullpen.

At the same time, the triumphs of guys like Crochet, López, and the rest of last year’s reliever-to-starter class prove it’s not impossible. Hopefully, this year’s class will have just as much success.