Brandon Webb is almost the last pitcher anyone would have expected to be idled for most of the season with an injury.

Through his first six seasons with the Diamondbacks, Webb was one of the most durable pitchers in baseball — averaging 219 innings a season. He’s also been one of its biggest winners with 70 victories over the last four seasons.

Webb, 30, has been a mainstay in the Arizona rotation since 2003, when he finished third in the NL Rookie of the Year voting. In addition to winning the Cy Young in 2006, he finished second in both 2007 and 2008.

The three-time All-Star’s career has been built around taking the baseball every five days and almost always giving Arizona a good chance to win.

Last season, he was 22-7 with a 3.30 ERA, and Webb has been a workhorse for the D-backs. After being called up in April 2003, he made 28 starts and never made fewer than 33 starts in any season since.

But this season has been a nightmare for Webb, who made an Opening Day start and has been shelved ever since. He seemed to be making progress but on Thursday felt more soreness in the shoulder while throwing on a flat surface. Webb was going to throw a bullpen session on Friday in Seattle but the club sent him back to Phoenix for a third MRI on the shoulder to determine if he might need to undergo surgery.

Diamondback team physician Dr. Michael Lee is out of town and won’t be back until early next week. The team and its doctors have believed the problem exists outside of the shoulder joint and that the injury is not structural damage, but muscular in nature. They specifically have said it was a strained teres major muscle and that rest and strengthening would take care of the problem.

Tom Gordon, a pitcher on the Arizona staff, suffered a similar teres major muscle strain early in his career and told Webb the healing process was a long one. But not even rest and strengthening has helped Webb, who still suffers from stiffness and soreness in the shoulder.

That’s why the club wants another MRI to take another look at the labrum or rotator cuff. Webb is likely to get a second opinion no matter what the MRI reveals. He’s more frustrated than anybody else over the injury.

Webb’s rotator cuff was a concern in his senior year of high school at Ashland when he was shut down that spring with a shoulder injury. But a visit to renowned orthopedic surgeon Dr. James Andrews revealed it wasn’t a rotator cuff injury. Last season, the D-backs pulled a three-year, $54 million contract extension after multiple insurance companies raised concerns about Webb’s shoulder after looking at MRI results.

Webb went back to Andrews last December and was told the shoulder had only the normal wear and tear for a pitcher.

The MRIs have been consistent and mostly unchanged, not revealing any structural damage. But the D-backs want another look anyway.

The biggest long-term problem for Webb is that if he does require surgery, the Diamondbacks may not pick up the $8.5 million option for 2010. He’s in his last year under contract with Arizona. Webb would receive a $2 million buyout and become a free agent if the D-backs don’t pick up the option.

His value would be diminished unless he can come back and pitch at least a little this season. If it turns out he needs surgery, the 2009 season would be a lost one for the Ashland native and it would likely hurt him on the free agent market.

Until the MRI results are read and opinions offered sometime this week, Webb’s future — both immediate and longer — remains in limbo.

MARK MAYNARD can be reached at mmaynard@dailyindependent.com or (606) 326-2648.