Source: Aaron Gleeman, NBC Sports 
During the regular season the Red Sox ranked sixth among AL teams in runs allowed and the Cardinals ranked fifth among NL teams in runs allowed, but overall totals can be misleading when it comes to evaluating the quality of a playoff pitching staff because lesser pitchers rarely make an appearance.
For instance, through 11 playoff games for the Cardinals and 10 playoff games for the Red Sox both teams have used four starting pitchers.
That in itself is obviously a big change from the regular season and in the Red Sox’s case they’ve significantly shortened the bullpen pecking order too, essentially going with a four-man relief corps in anything resembling a high-leverage situation.
Adam Wainwright: 242 IP, 2.94 ERA, 2.80 xFIP
Michael Wacha: 65 IP, 2.78 ERA, 3.36 xFIP
Joe Kelly: 124 IP, 2.69 ERA, 4.19 xFIP
Lance Lynn: 202 IP, 3.97 ERA, 3.66 xFIP
Jon Lester: 213 IP, 3.75 ERA, 3.90 xFIP
Clay Buchholz: 108 IP, 1.74 ERA, 3.41 xFIP
John Lackey: 189 IP, 3.52 ERA, 3.49 xFIP
Jake Peavy: 145 IP, 4.17 ERA, 4.03 xFIP
Adam Wainwright is the best starting pitcher in this series and based on how he’s pitched so far in his brief MLB career Michael Wacha has made a strong case for second-best, but Jon Lester also has a lengthy track record of very good work and Clay Buchholz had a 1.74 ERA in the regular season.
I’d give St. Louis a slight rotation edge based on the Wainwright-Wacha one-two punch, but in the (likely) three-four spots I actually trust Boston’s Lackey-Peavy duo a bit more than Kelly-Lynn. *