Hanson felt some discomfort during the All-Star break and then experienced relief for nearly two weeks after taking a Dose Pack. But during the third inning of Monday's win over the Marlins, he experienced what he described as a spasm or muscle strain in his lower back.
"I'm not concerned," Hanson said. "I'm definitely frustrated. I don't want to miss any starts. But considering everything and what we need to do as a team, it's going to work out better this way. I feel like it should be fine after taking these weeks off. Then I should be fine for the rest of the season.
"I know it's not a big deal. It just bothered me a little bit, and I've got to get it right for the rest of the season."
Hanson will not be eligible to be activated until Aug. 15. This means he will likely miss two starts, both of which will likely be filled by Kris Medlen.
"Sometimes during the season when you have these little nagging injuries, you can never catch up," Braves general manager Frank Wren said. "You never quite feel right. We feel like putting him on the DL at this time will get him right by the middle of August, and then we'll have him for the stretch run."
Hanson has progressed through this season without any problems with his right shoulder, which forced him to miss most of the final two months of the 2011 season. But he has created some cause for concern while posting a 7.45 ERA and issuing 16 walks in the 19 1/3 innings he has completed in his four starts since the All-Star break.
"I felt like [my back] wasn't bothering me," Hanson said. "So that was never an excuse of mine. Looking back, it could explain it. But it wasn't bothering me. I wasn't feeling any pain or anything like that. It could have played a part, but I don't think it did."