One thing to remember when you consider how many innings the new rotation might save the pen in 2011 is that in 2010 the bullpen threw less innings than any other team in the National League. Phillie relievers tossed just 421 innings last year, the fewest in the league by a fairly wide margin. The Arizona Diamondbacks were 15th in the NL in bullpen innings pitched with 439. The Giants were 14th, and they threw 461 innings in relief — 40 more than the Phillies. Only one team in the DH-loving AL threw fewer innings in relief. The Mariners called on their pen to throw 419 1/3 innings, which was 1 2/3 less than the Phillies.

So even before adding Cliff Lee to the rotation, and even without a full year of Oswalt, the Phillies were already calling on their bullpen to throw fewer innings than any team in their league and almost any other team in baseball.

For the last three seasons, the Phils have been in the bottom half in the NL in terms of innings pitched in relief. In two of the three years they have been among the three teams that threw the fewest innings in relief.

Here’s the number of innings the Phillies bullpen has thrown per season over the past five years and their rank in innings pitched in relief in the NL for that year:

Year IP in relief NL rank innings pitched in relief
2010 421 16
2009 492 9
2008 483 14
2007 520 8
2006 539 4

In 2006, the Phillies threw 539 innings in relief. Only three teams in the NL threw more innings in relief that year, the Mets, Nationals and Cubs. By 2008, only two NL teams (the Brewers and the Diamondbacks) threw fewer innings in relief than the Phils. In 2010, the Phils were 16th in the 16-team league in innings pitched by their relievers (no NL team threw fewer).

There is bad news, though, and that’s that the bullpens, with one notable exception, have generally not gotten better at preventing runs as the number of innings they throw relative to the rest of the league goes down. The table below has the same three columns as the table above, but adds the NL rank for runs allowed per inning in relief for each year.

Year IP in relief NL rank innings pitched in relief NL Rank R/IP in relief
2010 421 16 8
2009 492 9 9
2008 483 14 1
2007 520 8 13
2006 539 4 3

In 2006, the bullpen was throwing a ton of innings, but they were also allowing fewer runs per inning pitched in relief than every bullpen in the league except for the Mets and the Padres. Last year the bullpen threw fewer innings than any other team in the league, but their effectiveness in terms of runs allowed per innings pitched was in the middle of the pack. 2008 is the only year in the last four in which the bullpen excelled at preventing runs. In that year the Phils were near the bottom of the league in bullpen innings pitched and at the very top in terms of runs allowed per inning pitched. You may recall that things turned out well for the team that year.

JC Romero appears to be headed back to the Phils. Five guys in the pen at this point: Romero, Baez, Contreras, Madson and Lidge. Many articles, including this post, suggest that the addition of Romero makes it less likely the Phils would bring back Durbin.