Bumgarner has struggled in the postseason this year. After finishing the regular season with a 16-11 record and a 3.37 ERA, the young pitcher has given up a combined 10 earned runs in eight innings this postseason. He last pitched in the Game 1 loss of the NLCS against the St. Louis Cardinals, giving up six runs off of eight hits and a walk in just 3.2 innings.
The Detroit Tigers were just 26-25 against left-handed starters this season, which might have helped push Bumgarner into the starting role over Lincecum. Lincecum has mostly come out of the bullpen during the postseason, although he did start against the Cardinals in a 8-3 Game 4 loss. He gave up four runs in 4.2 innings in the effort.