Let's not pretend hitting for Shaw is an everyday occurrence, nor is he sitting against all lefties. He has played in every game the Sox have played this year (71), and has started 68 of them. Shaw has been pinch hit for 6 times this year, with 4 of those in the first 10 days of the season. Since then, the ONLY times he has been hit for were on June 14th (Rutledge) against the O's Zach Britton (this one was questionable since it was Rutledge) and Monday against Duke (Pedroia). The latter I can understand since Duke does appear to be very tough on lefties and you had a .300 hitter in Pedroia available. He was not hit for last night, he came out because the ankle was bothering him from fouling a pitch off of it on Tuesday.
No matter how you want to spin it, the facts are that this year he is hitting lefties to the tune of .204 with and OBP of .250 and a slugging percentage of .347 and that includes the 3 hits over the past 2 games.. Yes he hit them well last year (in 85 plate appearances). He has not hit them well this year (in 52 plate appearances).
Now I will agree there are definitely better in game managers.