Overworked Pen, Revisited

At the beginning of July, I wrote that the Pirates have gone to their bullpen a lot, and that this raised concerns about the relievers' durability over a 162-game season. The team's top four relievers at the time--Arquimedes Caminero, Jared Hughes, Mark Melancon, and Tony Watson--had appeared in more games, and pitched more innings, than any top four in the National League. However, I noted that the Pirates relievers were unusually efficient, with all throwing a below-average number of pitches per inning. As a result, they hadn't thrown as many pitches as many of their peers, reducing the concern about wear and tear.

I decided to revisit this analysis as we enter the last month-plus of the season. I expanded my net, looking at each team in the majors. For each club, I identified their top three relievers, not in terms of games pitched, but in how they're used. FanGraphs' RotoGraphs column each week has a "Bullpen Report" that lists the top three relievers for each team. For the Pirates, for example, the closer is Melancon and the top two setup men are Joaquim Soria and Watson. For each team, I calculated, for the top three relievers:

• The number of games in which they've appeared
• The number of batters they've faced (a superior measure to innings pitched, which measures only outs)
• The number of pitches they've thrown

I included only relief appearances for pitchers who've moved from the starting rotation to the bullpen. For pitchers who've been traded, like Soria, I used their full-year statistics. This analysis makes bullpens that've had upheaval through injury (e.g., the Braves, who lost closer Jason Grilli for the season in mid-July to a ruptured Achilles) or roster changes (e.g., the Mariners, who released closer Fernando Rodney over the weekend) seem well-rested, since more lightly-used relievers may have moved into more prominent roles. I don't worry about that; somebody's who's thrown only 30 innings is, in fact, likely pretty well-rested.

Here are the 12 bullpens whose top three relievers have appeared in the most games:

1. Pirates (Melancon, Soria, Watson) 176
2. Cubs (Rondon, Strop, Hunter) 170
3. Rangers (Tolleson, Diekman, Dyson) 168
4. Phillies (Giles, Garcia, Gomez) 164
5. Cardinals (Rosenthal, Siegrist, Cishek) 162
6. Angels (Street, Smith, Salas) 161
7. Marlins (Ramos, Dunn, Morris) 161
8. Mets (Familia, Clippard, Torres) 161
9. Yankees (Miller, Betances, Wilson) 160
10. Brewers (Rodriguez, Smith, Jeffress) 159
11. Indians (Allen, Shaw, McAllister) 156
12. Royals (Holland, Davis, Herrera) 153

Other contenders: Astros (Gregerson, Neshek, Qualls) T13th, Orioles (Britton, O'Day, Brach) 17th, Giants (Casilla, Romo, Strickland) 18th, Dodgers (Jansen, Johnson, Baez) 21st, Nationals (Papelbon, Storen, Janssen) T22nd, Twins T24th, Blue Jays (Osuna, Sanchez, Cecil) 27th.

Granted, it's a strain on a pitcher to appear in a game, as it entails both warmup pitches and live pitches. But there's more strain in coming into a game with one out and a runner on first and allowing two more batters to reach before retiring the next two compared to getting the first batter faced to ground into an inning-ending double play. So the number of batters a reliever faces is probably a better indicator of usage than the number of games in which he appears. The top three relievers for these teams have faced the most batters:

1. Phillies 740
2. Rangers 698
3. Pirates 671
4. Cubs 670
5. Mets 667
6. Cardinals 655
7. Red Sox (Tazawa, Machi, Ognado) 642
8. Orioles 640
9. Angels 635
10. Indians 632
11. Reds (Chapman, Hoover, Mattheus) 625
12. Yankees 621

Other contenders: Astros 21st, Dodgers 22nd, Nationals 24th, Giants 25th, Twins 26th, Blue Jays 28th.

Finally, as I pointed out in July, efficiency can reduce strain on relievers' arms. So far this year, relief pitchers have averaged 3.9 pitches per batter faced. That figure ranges between 3.7 for the Giants, Twins and Pirates to over 4.0 for the Rangers, Rays, and Yankees. Spread over a few hundred batters faced, those extra pitches can wear a pitcher down. These teams' top three relievers have thrown the most pitches this year:

1. Phillies 2,848
2. Rangers 2,694
3. Cardinals 2,669
4. Pirates 2,623
5. Mets 2,618
6. Yankees 2,556
7. Indians 2,545
8. Cubs 2,535
9. Reds 2,529
10. Orioles 2,523
11. Red Sox 2,413
12. Angels 2,412

Other contenders: Royals 16th, Dodgers 22nd, Astros 23rd, Giants 24th, Twins 25th, Nationals 26th, Blue Jays 28th.

So what are the takeaways here?

• The Pirates have used their relievers a lot. However, the figures shown above are skewed by the addition of Joakim Soria. If I substitute Jared Hughes (the Pirates' No. 3 reliever before they traded for Soria on July 30) for Soria, the Pirates are still No. 1 in games pitched and rise to No. 2 in batters faced, but they fall all the way down to tenth in pitches thrown, behind both the Cardinals and the Cubs. They remain one of the most efficient bullpens, in terms of pitches per batter, in baseball. 
• To expand on that, the only Pirates relievers who have averaged more than the major league average of 3.9 pitches per batter are Antonio Bastardo (4.4) and Soria (4.6 with the Pirates, 4.2 with the Tigers). That being said, of the 100 relievers who have thrown the most pitches this year, only three teams have six on their current roster: the Pirates, Cardinals, and Rangers.
• The teams toward the bottom of the lists, notably the Blue Jays, Giants, Nationals, and Astros, in my opinion, seem to have particularly well-rested bullpens heading into September.