A two-hour arthroscopic surgery operation repaired a torn tendon in the rotator cuff of Robert Guerrero’s left shoulder on Tuesday while also determining that the fighter had “aggravated” an already existing condition, Guerrero’s manager Bob Santos, told RingTV.com.

Guerrero had been preparing to face Marcos Maidana for what the WBA calls its “regular” junior welterweight title, but had to pull out of the Aug. 27 bout after he injured the shoulder while throwing a punch during sparring two weeks ago.

A team physician for the San Francisco 49ers, operating Dr. Michael Dillingham said “that he’s very optimistic, and he feels that they did the best job that they could,” said Santos.

“As it turns out, Dr. Dillingham said that looking at the shoulder now, there’s no doubt that that it didn’t happen in the sparring sesssion,” said Santos.

“Dr. Dillingham said that the sparring session may have aggravated it and may even have torn it to more of a degree than it already had been, but he said that there is no doubt that Robert had been fighting for years with that tear in the rotator cuff.”

The 28-year-old Guerrero (29-1-1, 18 knockouts) must refrain from even light exercise for four weeks and could be out of the ring for as long as six months.

A two-time IBF featherweight and one-time IBF junior lightweight beltholder, Guerrero was after his 14th consecutive victory and his 10th knockout during that run against Maidana (30-2, 27 KOs).

Guerrero last suffered defeat by a split-decision to Gamaliel Diaz in December 2005 but won their rematch with a sixth-round knockout in June 2006..

Guerrero will be in the shoulder sling for about two weeks before he shadow box and then gradually move on to more rigorous training.

ORTIZ SPARRING WITH FORBES

WBC welterweight beltholder Victor Ortiz (29-2-2, 22 KOs) has been sparring with former IBF junior lightweight beltholder Steve Forbes in preparation for his defense against Floyd Mayweather Jr. (41-0, 25 KOs) on Sept. 17.

A crafty, slick-boxing, 34-year-old welterweight, Forbes has gone the distance with ex-world titleholders Oscar De La Hoya and Andre Berto, and owns a victory over current IBF junior middleweight strap holder Cornelius Bundrage.

“Steve Forbes has been doing a great job. We’re trying to emulate Floyd Mayweather, but what Mayweather does is pretty hard to [emulate,]” said Ortiz’s trainer Danny Garcia.

“Mayweather fights a different way than almost everybody. But we’re trying to do the same things. We’re trying hard to get ready.”

A former junior welterweight who debuted at 147 pounds by dethroning Berto (27-1, 21 KOs) by unanimous decision, Ortiz weighed “about 154 or 156 pounds” on Monday, said Garcia.

“That’s about where we want him to be right about now. We’re going to use a few different styles,” said Garcia.

“Victor will go forward, he’ll move back and box, or he can stay in the middle of the ring and fight. We don’t know if Floyd’s going to want to go forward or backward, but we’re going to be ready for anything that he does.”

Lem Satterfield can be reached at [email protected]