Thomas, who missed much of the past two years with ankle and foot injuries and has been on the DL this year with a strained quad, singled with two outs in the top of the 11th inning Thursday to give Oakland a 5-3 lead. It seemed like a perfect time to get the big man out of the game, and Macha was ready to send in Chavez as a pinch-runner.
"Chavvy had a helmet on and everything," Macha said Friday at Fenway Park.
That's when athletic trainer Larry Davis stepped in, reminding Macha that if Chavez eventually does end up on the DL, an appearance in Thursday's game could have cost the team an extra four days without him.
Chavez, who is sitting out the series with tendinitis in both forearms, hasn't played since last Sunday, so if he's placed on the 15-day DL before appearing in another game, the A's can make the move retroactive to Monday. That would make him eligible to return from the DL when the team gets back from its current road trip on July 24.
"We're still hoping to avoid the DL," Macha said, "but at the same time, you want to make sure that we're smart about it if we do decide to use it."
Asked why another player wasn't used to pinch-run for Thomas, Macha said he didn't want to use infielder Marco Scutaro or catcher Adam Melhuse because they were the only backups at their position.
Asked why a starting pitcher -- Dan Haren, for instance -- wasn't used, Macha said, "I think you're putting a guy in jeopardy for injury there."
First things first: With Dan Johnson at Triple-A Sacramento, most of the playing time at first base will go to Nick Swisher. Some, however, might go to Melhuse and second baseman Mark Ellis.
Melhuse has taken ground balls at first sporadically this year, but Macha said he'll start working more extensively with infield coach Ron Washington. And Washington said Ellis, who made two appearances at first base in 2005, would be far from a liability there.
"Mark's an athlete, and a smart one, too," Washington said. "If he can play up the middle in the big leagues, you know he can play him some first base."
As for Swisher, who played first base quite a bit in college, Macha suggested that he's a work in progress at the position.
"He's got a lot to learn over there, but he works hard at it and absorbs it," said the skipper. "He's got a little more range than [Johnson], but we're probably gonna have to live through some mistakes."
Said Swisher: "I'm comfortable there, but I can definitely get better. And you know that anyone who works with Wash will get better."
Dribblers: Milton Bradley started in right field and batted seventh in his first game back from the DL, with Jay Payton getting the nod in left. Bobby Kielty, who was batting .354 (23-for-65, three homers, 14 RBIs) over his past 19 games, did not seem bothered by not being in the lineup. "I've been to Triple-A twice this year," he said. "This is still better than that." ... Since losing 14 of their first 22 one-run games, the A's had won 10 of their past 11 such contests. ... Sacramento outfielder Hiram Bocachica hit two homers for the River Cats on Thursday, the second one a walk-off job that gave him five RBIs and boosted his batting average on the year to .331. He also was named the Pacific Coast League Player of the Week for the previous week. ... Catching prospect Kurt Suzuki went 2-for-4 with a double and a homer Thursday at Double-A Midland, raising his batting average to .299.
Coming up: A's righty Dan Haren (6-7, 3.52 ERA) takes on Red Sox righty Curt Schilling (10-3, 3.60 ERA) in the third game of the series Saturday. The first pitch is set for 4:05 p.m. PT.
Mychael Urban is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.