Brandon wrote an article about the upgrades to the Twins rotation, their potential impact on the Twins record, and some suggestions for further off-season moves. His analysis was WAR based, and, not to steal his thunder, he predicted that adding Worley, Correia, Pelfrey and Gibson to the rotation next year will add a few wins, but not enough to really matter. I decided to do similar analysis, but rather than look at WAR, I'm specifically looking at overall run prevention.
First, some general information about last season. The average American League team gave up 712 runs last season, for a 4.43 runs per game average. The Twins gave up 832 runs, for a 5.51 runs per game average.
Here is the damage done by Twins' pitchers last season who will either definitely not be back, be kept in AAA, or hopefully improve next season (I'm looking at you Hendriks).
|Brian Duensing (as starter)||52||47|
As you can see, these 10 pitchers threw only 40% of the innings last year, but gave up over 52% of the runs. Their overall rate was 6.75 runs per game.
Now put on your rose colored glasses pretend that Correia, Pelfrey, Worley and Gibson give up on average about 5 runs per game. This is a little bit worse than league average, but not unreasonable (this is essentially how Cole DeVries performed last year). Also, let's assume Gibson picks up 100 of the above innings, and the other three each pick up 160 innings (again, not completely unreasonable). By shifting from a 6.75 runs per game rate to a 5 runs per game rate, the Twins would only give up 322 runs in those 580 innings instead of 435, for a net gain of 113 runs.
For the final act of magic, I'm going to calculate how much this will improve the Twins' record next season. First, assume that all the other Twins pitchers match there 2012 performance. So instead of giving up 832 runs, they would only give up 719. Second, assume that the Twins score as many runs as they did last year, which was 701. Plug these two number into a Pythagorean Winning Percentage Calculator, and the Twins would be expected to win 79 games - a 13 game improvement!
Now, I understand that these calculations required a bunch of hand waving and wishful thinking, and if given 79 as the over/under for the Twins next season, I would definitely take the under. However, I found this exercise quite useful for demonstrating who were the worse offenders in the Twins pitching staff, and the impact they had on the terrible season in 2012. Most of them have left, and we can only hope their replacements offer improvement instead of more or the same..