SAN DIEGO — In compiling baseball’s best record through the first 11 weeks of the 2007 season, the Red Sox have been the beneficiaries of extraordinarily good fortune when it comes to injuries.

Until now, the five pitchers who made up the starting rotation on Opening Day have made all but two of their scheduled starts. Two missed turns by Josh Beckett (finger blister) have been the only interruptions.

But beginning Tuesday in Seattle, the Red Sox will have to find someone to take Curt Schilling’s spot. Schilling can’t return from his stint on the disabled list, which will be made official today, and made retroactive to Tuesday of this week, until July 4 and there are no guarantees that he will be ready then, or, for that matter, that his weak shoulder won’t be problematic for the remainder of the season.

It helps, of course, that the Sox have a comfortable 10½-game lead in the American League East, by far the cushiest margin for any division leader. But Schilling’s condition is a reminder of how fragile a team’s position can be when injuries intervene.

The Sox are officially undecided about whom to promote to replace Schilling. The obvious choice would seem to be Jon Lester, whose return to the Red Sox rotation has seemed like a foregone conclusion for months.

But some in the organization caution that Lester hasn’t thrown as well as his numbers suggest at Pawtucket and contend the lefty would benefit from additional time at Triple A as he rebounds from his bout with cancer.

If the Red Sox believe that Schilling could return after missing just two turns, the case builds for Kason Gabbard. Gabbard has already made one fill-in start for the Red Sox this year, defeating Atlanta earlier this month.

It might provide better continuity for the entire organization if Gabbard got tabbed for the two starts, then returned to Pawtucket. Lester, meanwhile, could continue to build arm strength and polish his game, uninterrupted by a short-term promotion to Boston.

Less clear is Schilling’s future both in the short-term and longer.

While his shoulder issues are less troubling than, say, Jonathan Papelbon’s were late last season (Papelbon suffered from a subluxation of the shoulder joint), they nonetheless bear careful monitoring.

Already, the Sox have attempted to limit his wear-and-tear by giving him an extra day in 7 of his 15 starts this season. That Schilling still broke down despite the best intentions of the organization has to be considered at least mildly troubling.

It’s worth noting that the Sox tied for the American League’s best record in 2005 without significant contributions from Schilling, who was recovering from off-season ankle surgery, which set back his off-season preparation.

Moreover, the Sox are better positioned to handle the loss of Schilling than they were two seasons ago, now that Josh Beckett and Daisuke Matsuzaka are performing like front-line starters.

Still, the Sox would be far better served if Schilling rebounded from this setback and added his experience and playoff know-how to the club’s championship pursuit.

If this is merely a hiccup for Schilling, both he and the team will benefit from the layoff. Come October, he’ll have two fewer outings and a couple hundred fewer pitches on his 2007 odometer.

If, however, this proves to be symptomatic of something greater, Schilling’s value on the free agent market could be diminished. Already, some baseball executives would think twice before committing to a 41-year-old pitcher who, by his own admission, has never had a great physique. Schilling’s weight and conditioning were a concern this spring, and this recent episode might be interpreted by some as a possible extension of that issue.

For Schilling to join the ever-growing list of 40-something pitchers receiving contract extensions — a list including, but not limited to Jamie Moyer, John Smoltz, Greg Maddux — he’ll need to return to form.

Those decisions won’t be made until much later in the season. In that respect, Schilling, like the Sox, doesn’t have worry.

For now, at least.

smcadam@projo.com