Manny Pacquiao will undergo surgery on his injured shoulder following the defeat to Floyd Mayweather in Las Vegas on 2 May, it has been confirmed.

The Filipino welterweight, who simply could not contend with the speed and precision of his illustrious opponent, was comfortably beaten on points in a disappointingly one-sided affair at the MGM Grand and it was subsequently revealed afterwards that Pacquiao had suffered a tear in his right shoulder during preparations for the so-called 'Fight of the Century'.

Indeed, trainer Freddie Roach even went as far as to claim that his camp had considered postponing the contest at one stage although eventually decided against it after the problem showed signs of improvement after various consultations and tests.

"We have an MRI scan that confirms he [Pacquiao] has a rotator cuff tear. He has a significant tear," orthopedic surgeon Neal ElAttrache told ESPN.

"Once you know he has a tear that's not going to heal on its own, then the decision for an active person is you want to try to fix this before it gets bigger. If all goes as expected with the surgery and the rehab is successful, Manny could be back training in about six months.

"At that point, he will be regaining strength and endurance, and competition is reasonable within nine months to a year. But this is a severe enough tear that it won't heal without being repaired."

Pacquiao's adviser, Michael Koncz, added: "After speaking with the doctor, it was determined that the best method and approach is for Manny to have surgery. Manny is doing OK."

As well as hampering his tactical approach against Mayweather, Pacquiao's injury has been the source of great controversy in recent days due to an apparent dispute over the lack of a pre-fight painkilling injection.

A joint statement released by promoter Top Rank claimed that the United States Anti-Doping Agency was notified both of the shoulder issue and the specific medication being used to help before the main event, but was disappointed with the decision to halt treatment.

"USADA spoke to Manny's doctors twice, investigated, and confirmed in writing that the proposed treatments, if used, were completely allowed," they said. "The medication approved for fight night was a non-steroidal anti-inflammatory (Toradol).

"Manny continued to train and his shoulder improved, though not 100%. This is boxing, injuries happen, and Manny is a warrior. Again, in consultation with his doctors, promoter and advisers, Manny decided to proceed with the fight anticipating that he could receive his pre-fight treatment. That specific treatment had been approved by USADA in writing at least five days before the fight.

"On his pre-fight medical form filled out earlier in the week, Manny's advisers listed the medications that Manny used in training and the medications that might be used on fight night. A few hours before he was expected to step in the ring, when Manny's doctors began the process, the Nevada Commission stopped the treatment because it said it was unaware of Manny's shoulder injury.

"This was disappointing to Team Pacquiao since they had disclosed the injury and treatment to USADA, USADA approved the treatments, and Manny had listed the medication on his pre-fight medical form."

The issue, it seems, centres on those aforementioned medical forms. While Pacquiao's camp have been eager to stress that they did fully disclose details of the medication, the Nevada Athletic Commission claimed that they were unaware of any injury problems.

"Every fighter is given a [prefight] medical form to fill out," chairman Francisco Aguilar said. "He disclosed the medications, but he didn't disclose any injury. That's why we denied his request."

While the gracious Pacquiao has not wanted to place blame for the sixth defeat of his professional career solely on the condition of his shoulder, the prospect of a long layoff should all but end talk of a possible rematch.

Mayweather, now 48-0, has already confirmed that he plans to relinquish his world title belts ahead of one final contracted fight with American broadcaster Showtime in September, although he has yet to completely rule out the possibility of an attempt at breaking Rocky Marciano's record of 49 unbeaten contests.