I found an article on Fangraphs today that discussed the Tigers approach (or lack of) to rotational depth as we enter 2011. As we all know, Verlander, Scherzer, Porcello, Coke, and Penny have been written in stone. There are no battles this spring to get a spot in the rotation. No matter how well Oliver, Turner, Furbush, Below, or anyone else does, it will take injury or major meltdown to alter our plans.
The Fangraphs article seemed to question the approach of not really having much MLB-tested SP depth in the organization. Some of the comments discussed the need for additional SP during the course of the season. I wanted to find out how often each team needed to use a pitcher (or several) beyond their top five. Using baseballreference.com, I considered a team's "core rotation" to be the five pitchers with the most GS. After that, I just counted the number of other GS for pitchers outside of these five.
Obviously, not all of my rotations would be considered by true fans of the team as their 'A' rotation, but we're just looking at the number of pitchers needed beyond the five most frequent starters. The complete results are posted here.
There were some interesting findings. First, the average for all teams was about 28 games (17.5%). The Rays were pretty solid last year. They only need 8 additional starts (5%) beyond their core rotation. By contrast, the Nats had 54 (33%) games started outside of their core. We all know which team was more competitive.
Competitiveness does seem to be a factor. I averaged the six divisions. The first place team in each division needs additional starters about 13% of the time; second place was 14.8%; third place was 15.4%; fourth was 20.9% and fifth was 22.4%. Of course, there's a bit of a chicken and egg argument here. Do the cellar-dwellers use extra starters because they're crummy and are looking for answers or does the need for extra starters turn a team's season into a Pirates-esque scavenger hunt for starters? My guess is it's a little bit of both.
In conclusion, if you hope for your team to finish in 1st or 2nd place (which I do!), it's best if you assume that you'll need 20-25 games started outside of your core rotation. Right now, the Tigers don't have a strong contingency plan (Andy Oliver, I'm pointing at you), but I don't feel that many other teams do either. As it stands, I think Andy Oliver can perhaps be as good as anything we might add to our team as a backup plan.