"Our manager has bad bullpen management," and "we lost x amount of games because of our bullpen management," are two very universal complaints among MLB fanbases. If you've followed along with the Pittsburgh Pirates this year, these are the two complaints that have come up ad nauseam with manager Don Kelly's bullpen usage. However, Kelly's poor bullpen usage may be over-exaggerated, as he is managing a bullpen in the hardest era to manage one.
The general advent of the bullpen as a whole is still a relatively new addition to baseball. The closer, as we know it today, basically did not exist for the first 100 years of baseball history. Stathead tracks historical data to 1871. The first reliever to record at least 30 saves would not be until 1965, and it would take until 1973 for at least ten relievers to have at least one 30-save season.
Given how recent bullpens are, it's unsurprising that there has been a lot of change in a very short amount of time. How bullpens are used has changed drastically in the last 10-15 years. In 2010, the average number of innings per start was around six innings. In 2025, the average start barely lasted five innings. There is a massive difference between managing the bullpen for just three innings on average and for four innings at a time.
More innings for relievers obviously means more relievers in general. From 2010 through 2015, 293 pitchers threw at least 100 innings out of the bullpen. That number has risen dramatically since. From 2020 through 2025, there have been 335 pitchers who have thrown 100+ frames out of the pen. That includes the shortened 2020, 60-game season.
Although teams utilize more relievers per season, reliever volatility is still very high. Front office execs, coaches, scouts, player analytics gurus, and player development staff are likely never going to crack the reliever code because even the best relievers only average about 65-75 innings a season. For a modern-day starter, they reach 70-75 innings by the end of May. The small sample size of innings pitched, combined with the sporadic usage for most non-closing relievers, means there's going to be a lot of season-to-season variance.
Another factor is reliever workload because of how hard relievers throw. Velocity has risen a ton among relievers. During Statcast's first season in 2015, the average fastball for relievers clocked in at 93.2 MPH. Now, the average fastball by a reliever comes in at 94.8 MPH. Change-ups and sliders now average out over 85 MPH for relievers, compared to 84 MPH and under in 2015.
Some Pirates fans may argue that former manager Clint Hurdle didn't have any problems managing the Pirates' bullpen when the Pirates went to the playoffs in 2013, 2014, and 2015. However, Hurdle also benefited from managing some historically good bullpens. The 2013 Pirates had five relievers who threw at least 50 innings with an ERA under 3.00. That is tied with the most by a single team in baseball history. That doesn't even encompass Jeanmar Gomez or Bryan Morris, both of whom had an ERA under 3.50 and threw at least 65 innings.
Although the 2014 Pirates' bullpen didn't make history, they still had a very solid core of relievers between Mark Melancon, Tony Watson, and Jared Hughes, all of whom pitched at least 60 frames with an ERA under 2.00. The 2015 Pirates were close to the 2013 Pirates, with four bullpen arms who posted sub-3.00 ERAs and 50+ frames. That also doesn't account for Arquimedes Caminero, who threw 74.2 innings with a 3.62 ERA, or trade deadline pickups Joakim Soria and Joe Blanton. Soria and Blanton threw a combined 61 innings with the Pirates, posting a microscopic 1.77 ERA while striking out 27.5% of opponents, and handing out a free pass just 7% of the time. They also allowed just a single home run between them.
Hurdle made very few mistakes with the bullpen during these three seasons because nearly all of his options were good relievers. Only one Pirates reliever ever had a season with an ERA over 4.00 from 2013 through 2015 while throwing 50+ innings. That was Justin Wilson in 2014, who posted a 4.20 ERA over 70 innings. Of course, Hurdle also benefited from starters going into games longer.
This isn't to say that Kelly should be forgiven for every single mistake he has made as a manager regarding the bullpen. However, it is a problem most managers suffer from because it is the hardest time ever to manage a bullpen. Starters are going fewer innings per start, bullpens are being relied on more heavily, there are more arms to choose from, and nearly all of them are very volatile. Plus, more hard-throwing relievers make workload management harder than ever. The next time Kelly makes a choice you don't like, remember that you're far from the only fanbase suffering from this.
