BOSTON — It’s unclear whether Curt Schilling will pitch again following his season-ending surgery set for Monday. What is clear, however, is this: Schilling won’t pitch again for the Red Sox.

Even if Schilling intends to pitch in 2009, he’ll have to do it elsewhere. Over the last two seasons, the Red Sox have paid Schilling more than $20 million and gotten only 24 starts — none this year — for their investment.

Factor in the ill-will that resulted from the conflicting diagnoses last winter and it’s impossible to imagine the Sox extending another offer, however modest or incentive-laden.

But if Schilling’s five-year stay in Boston is over, it would be impossible to overstate its significance.

Before Schilling arrived, the Sox were in the middle of an 86-year championship drought. In the next four years, they won two titles.

If Schilling wasn’t instrumental in winning two World Series, he was certainly critical. Set aside the 36 total wins he posted in the 2004 and 2007 regular seasons and focus on the fact that Schilling was 6-1 in the two postseasons combined.

To put that into perspective, those six wins are more October victories than Roger Clemens and Pedro Martinez had in Red Sox uniforms — combined.

“He made a tremendous impact here,” general manager Theo Epstein said. “He helped us win World Series. He certainly lived up to his end of the bargain and it was a very effective marriage while it lasted.”

“He came here at a time when we were aspiring to win a World Series,” said manager Terry Francona, “and he was as big a part of it as anybody. … He pitched some unbelievably big games here.”

Indeed, though Manny Ramirez was named World Series MVP in 2004 and the Sox would not have prevented being swept by the Yankees in the ALCS were it not for a stolen base by Dave Roberts, it was Schilling who was the star of the magical title run that month.

After winning Game One of the ALDS against the Angels, Schilling suffered a tear near the tendon in his ankle and was rocked in his first ALCS start, against New York. Thanks to a radical bit of experimental surgery, he came back to win Game Six in that same series, then won Game Two of the World Series.

But even before his postseason heroics, Schilling helped change the culture for the Red Sox.

From the day he was traded to the Sox in November of 2003, just a month removed from one of the franchise’s darkest moments — a Game Seven loss to the rival Yankees in the ALCS — Schilling made his intentions clear.

In a commercial spot he filmed for Ford Trucks, Schilling said he was going to Boston to “break a curse.” And, then, months later, he did.

Schilling took on — rather than hide from — the Red Sox’ history of near-misses and heartbreaking defeats, and vowed to help change it.

Until Schilling, this simply wasn’t done. Most veterans, upon being dealt to Boston or arriving as a free agent, would feign ignorance about the team’s past, or maintain a disassociation from it. Not Schilling.

He knew the franchise — or, at the very least, its fan base — had an innate inferiority complex when it came to the Yankees.

So Schilling exploited that. He famously said one of his goals in October of 2004 was to silence Yankee fans in their own ballpark.

“I’m not sure of any scenario more enjoyable than making 55,000 people from New York shut up,” he said.

Schilling wasn’t afraid, and on the mound it showed. As one of his generation’s best big-game pitchers — and owner of a 11-2 lifetime post-season record — he liked nothing more than a challenge.

It’s been said that the best players make their teammates better, and while it could be argued that that’s difficult for a starting pitcher to accomplish, of this there can be little doubt: big games made Schilling better.

With Schilling’s mix of experience — he already had been a World Series co-MVP in 2001 — and bravado, the Red Sox weren’t afraid anymore.

Five years after his arrival, the expectations for the Red Sox have changed. Now October isn’t something to dread, but to welcome.

For that alone, his impact on the organization has been enormous and his place in team history is assured.

smcadam@projo.com