Martinez was in the dugout when the change was made, so it clearly wasn't planned ahead of time. Usually, the 34-year-old goes to the batting cages between his at-bats to stay loose.
Once the inning ended, Martinez walked back to the Tigers' clubhouse on his own, carrying his own gear and bats.
"It's just been a little sore in my back, a little uncomfortable to swing on the right side," Martinez said. "It's just a couple days. It's a little tough. I've been out for a year, and I've been out there every day swinging, swinging, swinging.
"It's nothing to worry about. I guess you can call it like maintenance."
Martinez said the issue is not related to his recovery from left knee surgery a year ago. His big test for the knee was his swing against right-handed pitchers, since it puts more weight on his left leg.
"Honestly, I'm not even worried about the knee anymore," Martinez said. "The biggest challenge for me was to hit left-handed. ... I'm swinging the bat pretty normal, like I would during the season."
Martinez expects to play Thursday night against the Braves, who will start right-hander Julio Teheran. The Tigers aren't scheduled to see a lefty starter until Saturday, when they'll face Jays southpaw Ricky Romero in Dunedin, Fla.
"I'm going to go out there tomorrow and keep playing," Martinez said.
Wednesday marked Martinez's first game since last Friday, when he left after two at-bats against the Mets. Manager Jim Leyland said at the time that resting Martinez the last four days was planned, a pattern of gearing him up and then backing him off.
Jason Beck is a reporter for MLB.com. Read Beck's Blog and follow him on Twitter @beckjason. This story was not subject to the approval of Major League Baseball or its clubs.