Tuesday's 2-1 win at Arsenal in the Capital One Cup was the first Saints match the 19-year-old academy graduate has missed this season.
Ward-Prowse was taken off on a stretcher 69 minutes into Saturday's win at Swansea, although manager Ronald Koeman was hopeful he would be fit for the return to Barclays Premier League action against QPR.
However, scans have shown the midfielder has a fracture in his foot which will sideline him for the next 10 weeks, meaning he will be missing for Saints and the England Under-21s in the upcoming European Championship play-off with Croatia.
"We're very disappointed about that, but that's football and that can happen," Koeman said
"It's unlucky but okay.
"The boy has to keep going and it's difficult because he had a great start to the season, but it's part of the football and he will come back."
Source : PA
Source: PA