FORT MYERS, Fla. — Even before the Red Sox begin their exhibition schedule tomorrow afternoon, the composition of their roster hardly qualifies as much of a mystery.

For some time now, the “who” has been a rather forgone conclusion. Sometime between now and March 25, when they open their regular season in Japan, the Sox must essentially determine whether they’re going to trade Coco Crisp and settle on the seventh and final spot in the bullpen.

But the “where” aspect — or the makeup of the team’s batting order — is a little less settled.

Yesterday, the Sox unveiled not one but two lineups for the start of the exhibition schedule — the team hosts a day-night doubleheader with college teams tomorrow — and the regulars are fairly split between the two, giving the fans in attendance for the separate-admission games a chance to see a representative sampling of the major-league club.

Eventually, though, the Sox will have to choose one, and much of that decision will pivot on who wins the center-field job.

Though the Red Sox continue to insist that no determination has been made at the position, and go to great pains to emphasize that Crisp is the incumbent, all of the evidence suggests Jacoby Ellsbury will be the team’s center fielder — and sooner rather than later.

If Crisp is in the Opening Day lineup, it will be the result of one of two scenarios. In one, the Sox, having not found a taker for Crisp in spring training, will not wish to drive Crisp’s value down further by putting him on the bench. In the other, Ellsbury will struggle mightily in Grapefruit League games, highlighting the need for additional seasoning. The latter, by the way, is highly unlikely.

Should Ellsbury secure the spot, the Sox will have a second decision on him to make: Do they immediately entrust him to the leadoff position, or manage his introduction to life as an everyday player more carefully by placing him at the bottom of the order.

Last September and October, Ellsbury hardly looked overwhelmed by the leadoff assignment. He is a more patient and selective hitter than Crisp, and there seems little need to spoon-feed him the promotion to the top of the lineup.

If Ellsbury is, indeed, the leadoff choice, the remainder of the batting order falls into line without much difficulty.

Second-year second-baseman Dustin Pedroia seems the perfect man to hit second, as he excels at making contact — striking out only 42 times in 520 at-bats last season — and can hit behind the runners, enabling the Sox to take advantage of Ellsbury’s speed.

The three-four combination, of course, is automatic with the duo of David Ortiz and Manny Ramirez returning for their sixth season as the game’s most productive middle-of-the-lineup duo.

For much of last season, manager Terry Francona stayed with J.D. Drew in the fifth spot, despite Drew’s struggles. Francona liked the left-right-left flexibility in his 3-4-5 spots, but Drew’s poor first half may have, in turn, affected Ramirez, who took months to find his rhythm.

Eventually, Francona elevated Mike Lowell to the fifth spot — and cleanup, too, when Ramirez missed a month with an oblique strain. Lowell led the team in RBI and could hit either fifth or sixth, alternating with Drew.

If the Sox opt for the Ellsbury-Pedroia couplet at the top, Kevin Youkilis could drop to seventh. Youkilis’ ability to work counts, fight off pitches and wear down opposing pitchers was highly valued at the top of the batting order the last two seasons, but he may be of more help in the lower third since he has decent extra-base power (.453 slugging percentage last year) and can give the lineup additional depth.

That would leave Jason Varitek — or, every fifth day, Doug Mirabelli — as the projected No. 8 hitter, with Julio Lugo slotted ninth, where his speed (33-for-39 in stolen-base attempts) can be utilized to give the Sox a double-leadoff effect.

A more prominent role for Crisp, of course, would drastically impact the rest of the lineup and force Francona to select either Lugo, Pedroia or Youkilis as his leadoff hitter while Crisp likely occupied the seventh spot.

smcadam@projo.com