Mills said he's simply trying to take some pressure off Martinez, who entered Saturday in a 4-for-48 slump with no extra-base hits.
"I don't want to sit here and try to spin it any way that sounds good, but more than anything else I'm trying to take a little pressure of J.D. a little and see if that helps him," Mills said. "Maxwell is swinging the bat well against left-handers [lefty Derek Holland started for the Rangers] and I need somebody to hit third and I wanted to keep Jed [Lowrie] fifth."
Maxwell was hitting .350 (7-for-20) against left-handers entering Saturday, and with limited at-bats this year he knows how quickly his batting average can improve -- or suffer -- with one good day at the plate.
"It's funny when you have several at-bats and what a difference a week can make regardless of whether it's positive or negative," he said. "I'm trying not to upset my rhythm and get ready for whatever happens."
Matt Downs started at third base over Chris Johnson, who was hit by a pitch on Friday but is fine. Mills said he wanted to give Downs his first start since Tuesday in Philadelphia.