“It’s unfortunate for Josh but we can bring in Theo [Cabango] and it’s a real opportunity for him,” Rees said.
“He hasn’t had the game time he may have wanted in South Africa and the games before that, but he showed what he can do against Ulster. When you talk about potential in Welsh rugby, he is right up there.”
Cabango has been touted as a future Wales wing by his Cardiff coach Matt Sherratt, who compared the 22-year-old to Test regular Rio Dyer for pace and guile.
The Cardiff wing is eager to be the latest Arms Park product to make the step to international rugby this season.
“I’ve been proud to see so many friends get that call and the likes of Cam [Winnett], Alex Mann and Mason [Grady] have really taken to it,” Cabango said.
“It’s always been my dream to play for Wales. I guess this Saturday is a last chance to impress [before the summer] and getting that chance would be amazing.
“It’s always a good challenge against Ospreys. It’s usually pretty physical and they’re desperate to get a play-off spot. But we’ve also got something to prove.”