Berkman fielded grounders at first base, ran sprints in the outfield and took batting practice on Saturday. He reported feeling no discomfort in his left calf afterward.
"We were hopeful of having him [activated Friday], but he still didn't quite feel 100 percent," Mozeliak said. "But after what he's done today, all the feedback I'm getting has been very positive."
Berkman has been on the DL since April 19 with a left calf strain and has taken only 23 at-bats this season. The Cardinals are expected to ease Berkman back in by initially splitting his playing time with Allen Craig.
To put Berkman on the 25-man roster, the Cardinals will have to make a corresponding move. Bench players Shane Robinson and Matt Carpenter seem most at risk to lose their spot. Mozeliak said on Saturday that he already has "a pretty good idea of what we're going to do," but did not want to make that announcement public yet.