SCOTTSDALE, Ariz. -- The Giants face several tough decisions which hinge on one factor.

Bench roles must be claimed and bullpen spots must be won before the club's braintrust can finalize the Opening Day roster. But a seemingly unrelated element -- the anticipated durability of the starting rotation -- will influence which, and how many, reserves and relievers join the Giants to begin the season.

The Giants would prefer to open with an 11-man pitching staff. But this won't be feasible if the starters' Spring Training performances indicate that they can't regularly work deep into games. If manager Bruce Bochy believes that he'll be removing his starters in the sixth inning or earlier more often than he'd like, the Giants will be obliged to add a reliever and go with a more conventional 12-man staff. They'll probably do so anyway early in the season, since they have only two scheduled off-days between May 1 and June 17.

For now, signs are mixed. Tim Lincecum and Barry Zito both have worked six innings, a promising development. Matt Cain's Cactus League high is 5 2/3 innings, but he threw 90 pitches in his five-inning effort Tuesday against Arizona, showing decent arm strength. They have the wherewithal to pitch into the seventh inning and beyond. But the Giants also must consider their histories of accumulating inflated pitch counts, which inevitably shortens outings.

The Giants will watch Randy Johnson and Jonathan Sanchez carefully in their final two exhibition starts. Given Johnson's age (45), San Francisco shouldn't expect him to consume enormous quantities of innings. He lasted beyond six innings 13 times in 30 starts last season. Sanchez accomplished that feat 10 times in 29 starts. Moreover, neither Johnson, who skipped a turn due to biceps tendinitis, nor Sanchez, who couldn't build his pitch-count stamina while participating for Puerto Rico in the World Baseball Classic, has reached five innings this spring. Johnson admitted that when he makes his next start Sunday, he'll "have to get back to where I need to be, which is four or five innings."

Hence, the Giants have used various relievers in multiple-inning stints, since they lack a true "long reliever" who easily can work three innings or more when a starter departs early. It's obvious that the Giants are sincerely trying to make an 11-man staff work, at least until the first extra-inning marathon or double-digit outburst by an opponent taxes the bullpen and necessitates adding a reliever.

Until then, the Giants have three bullpen openings for seven contenders: left-handers Alex Hinshaw and Jack Taschner and right-handers Osiris Matos, Brandon Medders, Justin Miller, Luis Perdomo and Merkin Valdez. Ordinarily, Taschner would be included with Jeremy Affeldt, Bob Howry and Brian Wilson as locks to make the team. But the Giants have tried to trade Taschner, casting his status into doubt. Non-roster invitees Medders, who's unscored upon in eight appearances, and Miller, who yielded five runs in an exhibition against Team Japan but has recorded seven shutout Cactus League outings, have legitimate chances to stick. But at least one of them probably will be squeezed out by Perdomo, the Rule 5 Draft selection who must be kept on the big league club or be returned to St. Louis, or Valdez, who's out of Minor League options.

An 11-man pitching staff would give the Giants more leeway in deciding which six reserves to keep. Steve Holm is a near lock to be the No. 2 catcher, since third baseman Pablo Sandoval, who has extensive catching experience, hasn't spent an inning behind the plate this spring. Outfielder Nate Schierholtz, who's out of Minor League options, also is virtually assured of a job.

Add Eugenio Velez, the speedy, switch-hitting second baseman-outfielder, along with veteran infielders Rich Aurilia and Juan Uribe, and that leaves one spot on the bench. It could go to the "loser" of the Emmanuel Burriss/Kevin Frandsen competition at second base. But the Giants are growing increasingly fond of outfielder Andres Torres, the 31-year-old journeyman who's playing more like he's 21.

"They make me feel like I'm part of this team," Torres said recently.

That could be a fleeting feeling for Torres and a few others, depending on the size of the pitching staff.