The Phillies called on their relievers to throw 421 innings last season, which is not a lot. Not only was it the fewest number of innings pitched by a National League bullpen in 2010, it was the fewest innings pitched by any bullpen in the NL in the last five years.
The table below shows the NL team with the fewest bullpen innings for each of the past ten seasons and the number of innings they threw that season:
In 2005, three NL teams threw less than 421 innings in relief. The Astros threw 414, the Mets threw 413 and the Cardinals 397 2/3.
In 2002, the Diamondbacks threw 387 1/3.
Those four bullpens are the only four in the last ten years that went fewer innings over the season than the Phillies did in 2010. So while it sure seems like a full season of Oswalt plus the addition of Lee should mean fewer innings for the pen, I think there’s a question of how many they can drop given that their 2010 numbers were so low already.
The 387 1/3 innings that Arizona threw in relief in 2002 was the lowest number since the Braves threw 364 innings in 1998. So, if the Phillies threw 34 fewer innings in 2011 than they did in 2010, they would pitch 387 innings in relief for the year in 2011 and would be the bullpen that has thrown the fewest innings in the NL since 1998 (assuming no other team threw fewer than 387 in 2011). To throw 34 fewer innings in relief, they would need to throw about .21 fewer innings per game over 162 games, which is less than one out per game.