Schmidt will sit out the season

The drubbing the Dodgers experienced Wednesday during a 12-1 loss to the Toronto Blue Jays at the Rogers Centre served as only a precursor to the day’s most unsettling development for an increasingly brittle pitching staff.

Most players had already filed out of the clubhouse by the time Dodgers officials learned that pitcher Jason Schmidt would be sidelined for the rest of the season because of a variety of issues in his troublesome right shoulder.

The Dodgers had hoped that exploratory arthroscopic surgery Wednesday would reveal only some scarring and inflammation, but Dr. Neal ElAttrache found more extensive damage than anticipated during the procedure at the Kerlan-Jobe Orthopaedic Clinic in Los Angeles.

The most startling discoveries were a torn labrum and a frayed biceps tendon, which did not show up on an MRI exam. ElAttrache also found some scarring and inflammation in a bursa, which is a pad inside the shoulder that decreases friction between a tendon and a bone.

“We think this actually explains why he was having problems and why he couldn’t seem to get going,” said Stan Conte, the Dodgers’ director of medical services.

ElAttrache cleaned up debris inside the bursa and repaired the torn labrum and frayed tendon. Schmidt could resume throwing a baseball in three or four months and start pitching by spring training next year.

Schmidt never resembled the pitcher the Dodgers believed they were getting when he signed a three-year, $47-million contract in the off-season. The right-hander made six starts with the Dodgers, winning one, and finished the season with a 1-4 record and a 6.31 earned-run average amid a dramatic dip in his velocity.

“With all due respect, he hasn’t thrown well,” Dodgers General Manager Ned Colletti said. “It’s not as if he was on his way to a Cy Young season and suddenly you lost him.”

Chad Billingsley, a converted starter who has excelled as a middle reliever this season, will replace Schmidt in the rotation for at least the foreseeable future, making his first start of the season tonight against Toronto. Colletti said he would monitor the rotation over the next few weeks before deciding whether to target another starter or another reliever.

After making three middling starts and then going on the disabled list in April because of shoulder inflammation, Schmidt appeared to turn a corner and convinced the Dodgers that he was ready for a return to the major leagues during a May 30 rehabilitation start for Class-A Inland Empire.

“When I saw him in San Bernardino a couple of weeks ago I was encouraged because he was up to 90, 91 [mph] for a good portion of it

Schmidt pitched six scoreless innings against San Diego earlier this month before struggling so mightily in subsequent outings against Toronto and the Angels that the Dodgers put him back on the disabled list.

Nonetheless, Conte said there was no way to predict the extent of the damage to Schmidt’s shoulder without performing surgery.

“What we were seeing on the MRI was not what we were seeing clinically,” Conte said. “That’s why we made the decision to put a scope inside his shoulder to actually ... examine the shoulder from the inside.”

Schmidt also underwent shoulder surgery in 2000 to repair partial fraying of his rotator cuff, but Colletti said the Dodgers had no concerns about Schmidt’s durability when they signed him. Schmidt pitched 213 1/3 innings for San Francisco in 2006.

“Had we any inkling that this was going to be happening in the middle of June, I doubt if we would have went forward with it,” Colletti said of the signing. “You can’t predict. All you can do is look at previous performance, look at how many innings somebody throws, how many strikes they make, what an MRI shows. The MRIs are almost identical going back for a few years.”

ben.bolch@latimes.com