MIAMI -- It almost seemed inevitable that Alejandro De Aza would be barred from playing this season. On Monday, it became official, as it was announced that the young outfielder underwent right ankle surgery on Friday. The procedure was an arthroscopy -- a minimally invasive procedure in which the joint doesn't have to be fully opened -- and De Aza will miss the rest of the year.

De Aza, a Rule 5 Draft pick by the Marlins in 2004, hasn't played this season after suffering a high ankle sprain during the last inning of the last Spring Training game of the season. The 24-year-old center fielder collided with John Raynor on March 29 and was placed on the disabled list shortly thereafter.

In his rookie season last year, the six-foot lefty hit .229 with eight RBIs in 45 games.

Left-handed starter Andrew Miller (right knee tendinitis) threw an eight-minute bullpen session on Monday at Dolphin Stadium to follow one he threw last week in Jupiter, Fla., while the Marlins were in Chicago. The 6-foot-6 23-year-old expects to throw batting practice in Jupiter on Thursday.

"I'm feeling well," said Miller, who hasn't been running but has been spending a lot of time riding the elliptical bike. "I'm going to take three or four days off to rest up, and hopefully, I could pitch in games at some point. But nothing is written in stone.

"Everything they've got back there [in the trainer's room] they're using on me to try to get me back."

Catcher Matt Treanor (left hip strain) flew to Philadelphia on Monday to meet with groin-injury specialist Dr. William Meyers, who diagnosed Eagles quarterback Donovan McNabb with a sports hernia in 2005.

The club wouldn't reveal any information about Treanor's visit, but the 32-year-old is expected to be back in South Florida on Tuesday. And no matter what is decided in the near future, it's safe to say that Treanor's injury is worse than was anticipated when he went on the DL on July 8.

"In talking to [head athletic trainer] Sean [Cunningham], I guess that's a tough thing to diagnose," manager Fredi Gonzalez said.

In other injury-related news, Burke Badenhop (right shoulder tendinitis) had his next rehab assignment put on hold because of a stiff neck, and catcher Mike Rabelo (right wrist/foot) is not doing any baseball activity.