The 21-year-old, who is now expected to miss the start of next season, underwent surgery on his right fibula at the weekend.
Townsend told reporters at a press conference: "We're all gutted for Duncan. He's had a really good season and he'll be disappointed to miss the final few games.
"He's now on the road to recovery and we wish him all the best for his rehabilitation."
Weir was released from hospital on Monday.