Peter Diana, Post-Gazette With outfielder Jason Bay leading the way, the Pirates begin their first full-squad workout yesterday at Pirate City in Bradenton, Fla. Click photo for larger image.

BRADENTON, Fla. -- Although the Pirates' starting lineup is set, one issue still hovering this spring for manager Jim Tracy will be choosing a cleanup hitter.

It might float right into the season, too.

"It's flexible," Tracy replied yesterday when asked about the heart of his order. "It has the potential to be interchangeable."

Jason Bay, Tracy and other team officials agree, probably is best cast as a No. 3 hitter, largely because of his speed and, to a lesser degree, his ability to steal.

That leaves Jeromy Burnitz and Sean Casey, but in what order?

Over the past three seasons, Burnitz has had 334 at-bats at cleanup and batted .251 while averaging a home run every 24 at-bats. He has fared better in 716 at-bats at No. 5, batting .270 with a home run every 18 at-bats.

In the same span, Casey, most commonly a No. 3 hitter, has had 254 at-bats at cleanup and batted .299 with a home run every 42 at-bats. He, too, is better at No. 5, batting .341 with a home run every 25 at-bats.

Nothing clear there? There are other back-and-forth arguments, too:

Burnitz has better speed and is less likely to ground into a double play, so he might be better suited for cleanup.

Casey's .321 average against left-handers the past three years is far superior to Burnitz's .253, so he might be the stronger choice to hit higher.

Perhaps as a result of all this ambiguity, Tracy appears to be leaning toward examining the day's pitching matchup rather than entrenching anyone at cleanup.

"Are there people who could overwhelm you with a performance over the course of a season? Sure, there are," he said. "But the consistency of the group collectively, if everyone does what they're capable of doing, it has a chance to be fairly dynamic."

This much seems certain: Neither Burnitz nor Casey cares much.

"Not at all," Burnitz said. "Maybe for a while there I was a guy with a little bit of an ego who wanted to hit in the middle of the lineup, blah, blah. But that's years in the past, and I'm well over that. Eighth, fourth, who cares?"

"Wherever Trace puts me," Casey said, "that's where I hit."

Wells, Perez adjust

Pitching coach Jim Colborn has been working on delivery adjustments for starters Oliver Perez and Kip Wells. For Perez, it has been keeping the back leg steady. For Wells, it has been straightening his general posture.

Colborn's norm is to avoid multiple adjustments with any pitcher.

"I think you have one bullet," he said. "You'd better figure out what one thing you're going to say, and that's it. When we start shopping around, we get the pitcher confused."

Perez and Wells were among 17 pitchers who threw from mounds yesterday.

Buried treasure

All 62 players invited to major-league camp were present for the first full-squad workout of the spring. All except starters John Van Benschoten (shoulder stiffness) and Bryan Bullington (shoulder surgery) participated in all drills.

Starter Sean Burnett, coming back from two arm surgeries, had an extended -- and apparently effective -- outing off the mound after skipping a day at his request. "He's doing fine," Colborn said. "But we're going to continue to be cautious."

Bill Mazeroski returned to the field in his annual role as a special instructor. Kent Tekulve, the team's recently appointed advance scout, also showed up, but he will not begin instructional work until March 1.

Casey, on his first day with the Pirates after eight with the Cincinnati Reds: "It's definitely weird for me, putting on a different uniform. But it feels good. I've followed this emblem pretty much my whole childhood."