And the guy who plays the least -- shortstop Julio Lugo -- was back in there for the first time since June 14.
It was just one of those maintenance days for Francona, as injuries were not a factor in either lineup move.
"I just think that Bay's been out there grinding away," said Francona. "I think it's a good day to do it."
Considering it was a day game played amid typically sultry Atlanta conditions, Bay took the rare blow in stride.
"Too hot for a Canadian," quipped Bay.
Though Bay is just 2-for-12 against Braves right-hander Javier Vazquez, that wasn't a big factor in the decision. Bay is third in the American League with 19 homers and first with 69 RBIs.
"He hasn't had a ton of success, but to be honest with you, the way Bay is swinging, I'm not sure that really matters," Francona said. "I did know what he was. I wouldn't want to sit him against a guy he's like 7-for-10 off of."
The ultimate gamer, Bay had no issue with the decision to not start for the first time since May 28.
"Yesterday after the game, they said, 'I'm going to give you the day off tomorrow,'" Bay said. "I'm in no position to argue with the skipper, so it comes at a good time. National League game, I've been here before -- there's a good chance I'll get in. I wouldn't go into full relax mode just yet."
Bay doesn't really know how to relax on a game day. He played 162 games in 2005, 159 in '06 and 155 last year.
"For me, it's weird, because I'm out there most of the time. I don't really know what to do when I'm not playing," said Bay. "Guys always bust my chops, because I'm out there right away. 'Dude, go sit down, go inside, do something.' I can't. It's weird. Especially in a National League game, there's a chance I'm going to get in there. I'll relax the first half, but I'll be ready the second half."
Mark Kotsay replaced Bay in left field and batted fifth. David Ortiz batted cleanup for the second time in three games.
Then there is Lugo, who has gotten lost in the shuffle with Nick Green doing a solid job on both sides of the ball for Boston.
"Lugey, when he has been called upon, has actually swung the bat real well," Francona said.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.