How should the Pirates handle the rotation when Bubba Chandler gets promoted?

Pittsburgh Pirates top pitching prospect Bubba Chandler is off to an outstanding start to the 2025 season. He's only pitched 10.2 innings, but in that time, he's allowed two earned runs, striking out 18 batters with an extremely impressive 40.6% whiff rate. He has walked five opponents, but didn't allow a single free pass in his last outing. However, the most stunning development from his last outing was him hitting 101.5 MPH on the gun.

With how well Chandler is doing right now and considering how dominant the right-hander looked last season when he had a 3.08 ERA and 30.8% K% between Altoona and Indy, his debut will likely happen sooner rather than later. So when he eventually gets the call to the Majors, how will the Bucs handle the rotation?

Three pitchers—Paul Skenes, Mitch Keller, and Andrew Heaney —are pretty much safe from getting moved to the bullpen or lesser role. All three have had some solid outings this season, especially Skenes, and are here to be starting pitchers, not relievers. That leaves two who could either be traded or moved to the bullpen.

How will Pirates handle rotation logjam when Bubba Chandler is promoted for MLB debut?

Bailey Falter might be the prime candidate for bullpen duty. The southpaw put up a 4.43 ERA, 4.30 FIP, and 1.29 WHIP across 142.2 innings of work last season. While he had a respectable 7.6% walk rate and 1.07 HR/9, he only struck out 16.7% of the batters he faced. Falter struggled to limit hard contact as well, with a 90.1 MPH exit velocity and 8.9% barrel percentage. Underlying numbers did not like his body of work, with a 4.91 SIERA, 4.81 xERA, and 4.71 xFIP.

Some of those poor underlying numbers may be catching up to Falter. It has only been 15 innings, but he's already allowed a dozen earned runs. His exit velo (90.6 MPH) and barrel percentage (8.7%) are both similar to 2024. On the plus side, he's inducing swings and misses at a much higher rate. Last season, his whiff rate was only 19.8% (8th percentile), but is currently sitting at 29.8% (73rd percentile). Concurrently, his chase rate has dropped significantly from 27.8% (40th percentile) to only 20% (8th percentile).

One pitcher who has ample experience as a reliever is Carmen Mlodzinski. The right-hander spent his first two Major League seasons primarily being used out of the bullpen. He quietly put together a strong 2.91 ERA, 3.64 FIP, and 1.22 WHIP. His 22.2% strikeout rate was about league average, but Mlodzinski only allowed home runs at a 0.62-per-9 ratio with an elite 3.3% barrel rate. On the flip side, he only had a 10.2% walk rate.

Mlodzinski has made three starts so far this year. His first start saw him dominate through the first three innings before allowing four earned runs in the fourth inning, and he couldn't make it out of the frame. His second start was much more promising. He tossed five innings of one-run ball, struck out six, and only walked two. His third start also saw him allow four earned runs in 4.1 innings, but he still induced four K's with two walks.

In Mlodzinski's defense, he's getting insanely unlucky. His batting average on balls in play is .415, the fifth-highest of any pitcher who has started at least three contests. His 89.8 MPH exit velocity isn't great, but it shouldn't be high enough to cause a BABIP over .415. For reference, he had an 89.1 MPH exit velo in his first two seasons, but a BABIP of only .268. He also hasn't allowed a barreled-up batted ball yet; still, his high BABIP is being fueled by a 31.7% line drive rate.

But in due time, this will likely even out. No pitcher since 2003 has had a line-drive rate over 30% in 100 innings. Only five pitchers in baseball history have ever had a BABIP over .400 in even 60 innings pitched.

If the Pirates have to move one of Mlodzinski or Falter to the bullpen when Chandler is promoted, Falter may be the better choice for a role change. Mlodzinski has already shown more potential in a starting pitching role, even if he has more experience as a reliever. He has better stuff, is limiting hard contact better than Falter, inducing more strikeouts, and has a similar walk rate. He'll eventually adapt to going through the order a second time. Regardless of what comes next, getting Bubba Chandler into the rotation would be a huge boost to the pitching staff, even if it means pushing someone to the bullpen.