It's a blow for the 20-year-old, who made his international debut for Wales in Japan two years ago and has played two GUINNESS PRO12 games so far this season, starting against Edinburgh and Zebre.
However it now looks like he will be out of action until the closing weeks of the GUINNESS PRO12 season as he recovers from the surgery, and will be unavailable to Steve Tandy.
"We've done all the necessary investigations, discussed the findings with a specialist in London, and to ensure the best result for Daf the decision was for him to have surgery to repair a damaged tendon," said medical performance manager Chris Towers.
"He will have a slow recovery period because of the nature of the injury and is looking at four to five months before he'll be able to play again."
The Ospreys return to domestic action in the GUINNESS PRO12 this weekend with a derby clash against Cardiff Blues as they try to build on a promising start to their European campaign.
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