Lindstrom underwent an MRI and X-ray on Wednesday and was diagnosed with a muscle strain. He was put on medication to help him deal with the pain -- and Lindstrom said he's already feeling better.
"It's quite a relief to know that there's nothing really wrong," he said. "Everything's intact and I'm structurally sound. I'm going to keep getting treatment and take it day-by-day.
Lindstrom blew saves last Friday in Milwaukee and Tuesday against the Braves -- allowing a total of three home runs in those two outings. He had given up one home run previously. The back has been bothering Lindstrom just before he releases a pitch, causing him to fly open during his delivery. But, the closer has been trying to downplay the back's effect on his performance.
"It's something I've been dealing with," he said. "I'm pretty stubborn -- and I like to take the ball whenever the manager is going to give it to me. Did it affect me? Probably a little bit, but I thought I could get the job done, regardless. I still have my strength and stuff, but you don't realize how much you use your legs and lower half."
Manager Brad Mills said the Astros were going to be cautious with Lindstrom.
"We want to make sure he's absolutely 100 percent by the time he does go out there," Mills said. "We'll probably give the meds a little time to work. We'll see how he is on a daily basis, but really be as cautious as we can."