Swisher was drilled in the lower back with a 96-mph fastball from Curt Schilling in the sixth inning on Saturday and was still fuming about it after the game, saying he was certain the plunking was intentional.
Swisher still has an ugly welt where he was hit and was treated on Sunday with ice and electrical stimulation, but Macha said Swisher, who got over a case of food poisoning more than a week ago, didn't start simply because he needed some rest.
"He's got an energy-level situation where he needs a day off," said Macha.
Swisher's day of rest ended in the fourth inning, when he pinch-hit for designated hitter Frank Thomas, who let the game because he was sick. Swisher remained in the game for the rest of the afternoon.
Bradley responded to Swisher being hit by screaming at Schilling from the top step of the dugout and also got into it with some fans.
"With Milton, the reason he's not in the lineup in there is because he did a lot of baserunning the other day, and he hasn't played a lot of games lately," Macha said, referring to Bradley's 4-for-5 night on Friday and his recent stint on the disabled list. "He'll be back in there tomorrow."
Swisher was hit by Schilling an inning after A's starter Dan Haren hit Red Sox captain Jason Varitek with a pitch, and some of the comments made after the game suggested that Haren had hit Varitek in retaliation for Boston hitting Frank Thomas on Friday after a Barry Zito fastball grazed David Ortiz's finger.
"You probably could look at both sides and say there's some justification," Macha said.
Chavez update: Third baseman Eric Chavez sat out his fourth consecutive game, and while Macha wouldn't rule out his return to the lineup on Monday for the opener of a three-game series against the Orioles at Camden Yards, it doesn't seem likely.
"I talked to him for about 10 minutes on Saturday, and he's still a little frustrated," Macha said. "He's not feeling that he's quite there yet."
If the A's are going to put Chavez on the disabled list, it'll probably happen on Wednesday or Thursday. Teams can DL a player retroactively up to 10 days, as long as he hasn't appeared in a game, and Chavez last played on July 9.
Dribblers: Backup catcher Adam Melhuse got his second career start at first base on Sunday. The first came in September 2000, when he was with the Colorado Rockies. ... Center fielder Mark Kotsay suffered a bruised knee when he slammed into the wall on Saturday while making a tremendous running catch to rob Varitek of an extra-bases hit.
"That's one of the better ones I've seen here," Macha said.
Coming up: A's righty Jason Windsor will make his big-league debut on Monday when he takes on Orioles lefty Adam Loewen (0-2, 7.12) in the series opener in Baltimore. First pitch is scheduled for 4:05 p.m. PT.
Mychael Urban is a national writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.