Martinez took early batting practice and hit off a tee with hitting coach Mike Barnett watching closely.
Martinez had hits in his first two at-bats Tuesday, dropping a bloop double to right field in the first inning before rapping an RBI single in the third for his team-leading 50th RBI of the year.
"I just feel like I've been missing a lot of pitches lately because I've been under them so I wanted to work off the tee," he said. "I wasn't getting on top and that was the biggest thing. I'm getting in good counts and being patient and not swinging at many balls. I'm swinging at my pitches and fouling them off and that's what's killing me right now."
It's been nearly a year since Martinez made his Major League debut -- he was called up from Double-A on July 30, 2011, after the Astros traded Hunter Pence -- and he's come to understand he constantly has to make adjustments.
"It's kind of surprising a little bit," he said. "It's definitely adjustments on a regular basis. That's part of it, though. I feel like they're adjustments I can make. I haven't felt overmatched. For the most part, I feel like when I miss balls, I foul them off and that's not usually me."