Lester threw 100 pitches in his Game 1 loss, which was slightly lower than his season average (106). By bringing back Lester for Game 4, the Red Sox would then have the ability to pitch Josh Beckett in a winner-take-all Game 5 on regular rest.
And if the series does go the distance, the Red Sox would have their top two starting pitchers taking the ball in four of the five games.
Francona's Plan B would be Daisuke Matsuzaka starting Game 4, followed by Lester on five days of rest in Game 5.
Matsuzaka was available in the bullpen for Game 1, but he didn't pitch. He will again be there if necessary for Friday night's Game 2.
Meanwhile, Lester is fully aware of the possibility -- or maybe even probability -- that he will pitch Game 4, assuming the series extends that far.
"We've already talked to him," Francona said. "Obviously, we've got to see how we get through tonight. We get back at probably nine in the morning. So once we get through tonight, he may throw a side tomorrow. There's a decent chance.
"He threw, I think, 100 pitches. I think we'd like to bring him back [for Game 4]. I'm getting ahead of myself, but that would allow Beckett to pitch game 5. That's what we're hoping to do. We've got to get through tonight and make sure Lester is OK. If not, we'll throw Dice-K [in Game 4]. That was kind of the thinking all along, but we have to leave it open with some flexibility just to make sure everyone can do it."
The Red Sox lost Game 1, 5-0, though Lester pitched well, giving up three runs over six innings.
"I'd like another shot at them," Lester said on Thursday night. "Hopefully Josh and [Game 3 starter] Clay [Buchholz] can pick me up and I can have another shot."
Lester's only previous career start on three days' rest was on April 23, 2008, when he gave up nine hits and four runs over five innings in a 6-4 loss to the Angels. However, that was under very different circumstances. Beckett had been scratched because of an illness and Lester found out just hours before first pitch that he was taking the ball.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.