In his return to the lineup, Carpenter went 0-for-4 with a strikeout in a 1-0 win over the Braves.
"These guys are going right to the start of the dog days of August, but I feel like I'm coming out of Spring Training," Carpenter said. "My swing felt great before I got hurt, and it feels good now. One of the positives is you get a lot of rest. From a physical standpoint, strength and all that stuff, I'm ready to go."
Carpenter went 4-for-12 with a double, homer and four strikeouts with Springfield. He started three games at second base and the other at third. Carpenter is expected to move between the two positions with the Cardinals, though he'll likely continue to get most of his exposure at second with the way Jedd Gyorko has seized playing time.
"[Manager Mike Matheny] knows that I'm willing to go wherever they need me for that day," Carpenter said. "I expressed my willingness to do whatever helps us win. We've already kind of crossed that road."
In Carpenter's absence, the Cards used six different players in the leadoff spot. Re-establishing some continuity in that top spot is especially crucial now that the Cardinals have a void in the No. 2 hole due to Diaz's indefinite absence.
At the time of his injury, Carpenter led the NL with a .420 on-base percentage and ranked second with a .988 OPS. He was also on pace to become the first leadoff hitter in Major League history with more than 100 RBIs in a season. (Darin Erstad drove in 100 as the Angels' leadoff hitter in 2000.)
To clear a spot on the 25-man roster for Carpenter, the Cardinals optioned left-handed reliever Dean Kiekhefer to Triple-A Memphis. With Kiekhefer's departure, the Cardinals return to a seven-man bullpen.
"I think now that we've gotten past that 17-game stretch, I think we can handle it," general manager John Mozeliak said. "Obviously, we'll create flexibility if we need to, but hopefully, having the additional position player gives us that edge."
• Diaz and his wife, Dayara, welcomed their first child, Nathan, into the world on Friday. Both mom and baby are said to be doing well.
• The Cardinals launched a Spanish language Twitter account -- @cardenales -- on Friday in an effort to better connect with the team's Spanish-speaking fan base. The organization has also created a video topic page (Los Cardenales) on cardinals.com to house Spanish-language video features.