Barney last played Tuesday, extending his spring hitting streak to seven games, then was scratched from a split-squad game against the D-backs on Thursday with a sore side.
"It was just during batting practice," said Barney, who collected two hits in the Cubs' seven-run first inning Monday. "I felt it a little bit. It was enough to tell somebody. I'm not the kind of guy who likes to let people know when things are lingering.
"The MRIs came up negative, so that's good. "A little bit of a strain in there. Maybe a little liquid. We're just being a little careful. I'm good. Ready to go."
Barney took a couple of days off, then started cardio workouts Saturday, along with "twisting rotational" exercises before returning to baseball activity Sunday.
"I got in the cage and started throwing a little bit and doing all that [Sunday]," Barney said.
Barney has hit in every game he's played, and entering Monday, he was hitting .417 (8-for-19) with three doubles, a triple, and seven RBIs. The short absence balanced with careful attention to the games he's missed had Barney confident he can get his swing back in rhythm without missing a beat.
"You're watching games every day, so that's your visualization right there," Barney said. "It was only a few days, so hopefully your timing's there. And if it's not, take a few at-bats and get back into it."