Infielder Brendan Ryan was recalled from Triple-A Memphis. He and Aaron Miles likely will share playing time at second while Kennedy, who was placed on the 15-day disabled list, is out.

Miles started at second today against the Los Angeles Dodgers. Ryan started at third base and batted ninth on a scheduled day off for Scott Rolen.

"I'm guessing he'll be back in September, but I don't know," manager Tony La Russa said of Kennedy.

Kennedy said the knee had been bothering him the last few days and an MRI exam on Sunday confirmed the injury. The team will schedule surgery in the next several days.

"I knew it wasn't good," Kennedy said. "When you play sports long enough you know what hurts and what's injured."

He has struggled all year after signing a free-agent contract with the Cardinals, batting .219 with three homers and 18 RBIs in 87 games. But Kennedy had been playing better lately.

Kennedy had played in five straight games for the first time since the All-Star break, and somewhere in that stretch he hurt the knee. He's unsure how it happened.

"The last couple of days it's been rough getting going out there," he said.

Ryan, 25, has batted .339 in 25 games with two homers and five RBIs with the Cardinals. This is his fourth stint with the team this season.