The Pittsburgh Pirates’ bullpen might be better off than many think

At this point a year ago, many saw the Pittsburgh Pirates' bullpen as the strongest part of the team's depth chart. However, the opposite was true for the 2024 season. The bullpen ultimately ended up being one of the worst parts of the season and was one of, if not the biggest reason why the Pirates didn't surpass their 2023 win total.

The Pirates, meanwhile, haven't done much to make the bullpen better, at least on paper. Their most significant addition is veteran left-hander Caleb Ferguson, who may even get some starts in 2025. Although that may worry some, their bullpen may be better off already than many believe it to be.

A good portion of the Pirates' projected bullpen core from this point last year is still returning for 2025. David Bednar, Colin Holderman, Carmen Mlodzinski, and Kyle Nicolas will likely play large roles for the Bucs. They also re-signed Hunter Stratton, who looks like he's well on track to be ready for the 2025 season. Dennis Santana had a huge breakout midseason, and they have since added the aforementioned Ferguson to fulfill a high-leverage lefty spot.

A good stat to measure bullpen talent is Stuff+. Stuff+ is a stat that measures how 'nasty' a pitcher's offerings are based on factors such as velocity, movement, spin, arm angle, and release point. It is also on a similar scale as other "+" stats, such as OPS+ or wRC+, where 100 represents the average. This is a better measurement of bullpen talent than the bottom line, like ERA, FIP, or WHIP. Relievers pitch small sample sizes per season, with even very the best only tossing about 60-70 frames a season, so a few bad games can greatly influence these numbers. There is a weak correlation between year-over-year reliever ERA.

In 2023, the Pirates' bullpen had a combined Stuff+ of 100, which was only the 24th-best mark in baseball. However, in 2024, that jumped to 107, the seventh-best among all 30 teams. The Pirates did lose one big contributor in this stat: Aroldis Chapman, who had a 134 Stuff+ mark while logging 61.2 innings pitched. However, he isn't the only Pirates pitcher who tossed at least 30 innings out of the bullpen with a Stuff+ of 110 or greater. Bednar, Holderman, Nicolas, and Stratton will all return to the Pirates' bullpen in 2025. 

Pair of Pirates relievers on comeback trail will be integral in bullpen roles

A pair of Pirates relief pitchers who will be important to their bullpen in 2025 took huge steps forward in Stuff+. Carmen Mlodzinski saw one of the biggest spikes, going from just 87 in 2023 to 102 last season. Despite David Bednar's struggles, he gained ten points in Stuff+. His 128 mark was a career best. He also gained nearly a whole tick of fastball velocity, going from 96.6 MPH to 97.3 MPH, another career high.

The Pirates will also have some new arms at their disposal that bring strong stuff with them. Elvis Alvarado topped out at 101 MPH at Triple-A this year. Although he struggled with walks, he pitched exceptionally well in the regular season and the Dominican Winter League this offseason, with an improved BB% in the DWL. Another offseason addition who has potential in the eyes of Stuff+ is Peter Strzelecki, with a 101 mark for his career.

That's plenty of optimism without even factoring in some prospects who could help the bullpen out. Mike Burrows made his MLB debut in the Pirates' final series of the season, making a solid first impression. He put up a 108 Stuff+ rating. Braxton Ashcraft, another top prospect who could get moved to the bullpen, has multiple pitches that grade out as a 60 on the 20-80 scale, per Baseball America. They also project his fastball as above average.

Relievers are easily the hardest thing to predict in baseball. Emmanuel Clase put up an ERA under 1.00 in 2024 after having an ERA over 3.00 the previous season. The San Diego Padres' bullpen had a 3.80 ERA in 2023, lost key relievers Josh Hader and Nick Martinez, yet still put up a near-identical 3.78 ERA in 2024. The least valuable bullpen per fWAR in the Expansion Era (in a non-shortened season) is the 2007 Tampa Bay Rays with a -3.1 mark, along with a 6.16 ERA and 5.31 FIP. The very next year, they had a 3.55 ERA, 4.18 FIP, and +3.6 fWAR, ranking top 10 in the league in ERA and fWAR. While it's not a guarantee the Pirates' bullpen will suddenly be great again in 2025, they're setting themselves up by building their bullpen full of relievers with high ceilings. Sometimes, that's the best way to build a bullpen.

There is no such thing as an exact science when building a bullpen. We shall see how the Pirates' relievers perform in 2025. However, their current situation may not be as bleak as some believe.