Francona said he did not consider turning to closer Cody Allen for that critical at-bat.
"I get your point," Francona said. "But say Cody comes in and walks him. Let's say they pinch-hit. There's just a lot of unknowns. Shaw's been so good that it's just too easy to say that after the fact, because what if Cody came in and didn't get him, and then the righty [Nick Castellanos] took him deep?
"Cody's splits are the same way. Then, you're going, 'What are you doing?' [Shaw] just didn't make the pitch he needed to."
Heading into Sunday's finale in Detroit, Shaw (2.42 ERA in 73 games) had limited right-handed batters to a .155 average and .444 OPS, but lefties were batting .296 with a .795 OPS off the right-hander. For the right-handed Allen (2.12 ERA in 70 games), the splits are reversed: lefties had a .133 average with a .449 OPS and righties had a .250 average with a .766 OPS.
"He's devastating against righties," Francona said of Shaw. "I think it's a little bit like Cody. There's been some damage done to him with lefties that has skewed his numbers a little bit, because there's a lot of lefties in the league where you look up and there's not good numbers. With that cutter he has, if he throws a flat one, the lefties have a little better chance."
Avila beat Shaw on a 3-2 slider, which the pitcher left over the plate. Francona said Shaw's strategy -- with first base open at the time -- made sense.
"If you look, early in the count he got him to kind of wave at a breaking ball down," Francona said. "I think he was trying to do that again. Sometimes you try to use the open base to your advantage. He just left it up. I don't second-guess our guys too often. They've got a pretty good feel for what they're doing and [catcher Yan Gomes] really grinds at it."
Jordan Bastian is a reporter for MLB.com. Read his blog, Major League Bastian, and follow him on Twitter @MLBastian. This story was not subject to the approval of Major League Baseball or its clubs.