ST. LOUIS -- Despite an extra-inning win on Tuesday, the Pirates' seventh victory in eight games came at a heavy cost as the team lost starting catcher Ryan Doumit indefinitely to a thumb injury.

On the 15th pitch of the game, Doumit received an offering from starter Phil Dumatrait that hit Doumit's glove and fractured his left thumb, caroming away for a passed ball.

Dumatrait made one more pitch to Doumit before the inning ended. Doumit did not return, and after an examination by the Pirates' doctors, he was determined to have a slight fracture near the top of the left thumb.

"It hurt initially," said Doumit, who was making his 25th start of the season behind the plate. "I didn't know there was something wrong until the next pitch."

Doumit will return to Pittsburgh on Wednesday to have his thumb re-evaluated. He is headed to the 15-day disabled list regardless, but the biggest question is simply for how long.

"Obviously, it's not in the joint which is good," manager John Russell. "I actually had a guy last year who had [a similar injury], and it was 10 days to at the most three weeks. We're not sure yet. We'll see where we're at. Obviously, [it's] disappointing for everybody."

The loss of Doumit will create a large void in a Pirates offense that has finally begun to find some consistency. Doumit had found his niche as the team's cleanup hitter and was making his 18th start in the fourth hole.

For Doumit, this latest injury may be the most frustrating of the numerous ones he has endured. He has been criticized for being injury prone in the past, but Doumit came into Spring Training in the best shape of his career and parlayed his offseason work into earning the majority of playing time behind the plate over 2007 starter Ronny Paulino. Doumit had been lauded for his improvements defensively, and at the plate. Doumit entered Tuesday with a team-best .350 average.

Now his output is again put on hold.

"Obviously, it hurts. I don't even know what to say," said a visibly irritated Doumit. "It couldn't have come at a worse time. I'm tired of the clichés that everything will be OK. It's frustrating."

The 27-year-old catcher, who missed time last year with hamstring, wrist and ankle injuries, had hit safely in 13 of his last 14 starts. In that span, Doumit had 11 RBIs and a .393 average. His .364 average as a starter was tops among all Major League catchers.

Paulino will assume the starting catcher role in Doumit's absence. The Pirates will also be calling up a another catcher -- likely to be either of Triple-A Indianapolis' two backstops, Michel Hernandez or Raul Chavez -- on Wednesday to serve as Paulino's backup.