The Warriors came out 27-17 victors that day but it came at a cost as Weir joins an already long list of injury casualties at Scotstoun - with DTH van der Merwe, Chris Cusiter, Moray Low, Rob Harley, Ed Kalman and Pat MacArthur all facing time out.
And while Townsend admits Weir's news couldn't have come at a worse time with his Glasgow side kicking off their Heineken Cup assault with clashes against Northampton Saints and RaboDirect PRO12 rivals Ulster, he is aware that the season is a marathon and not a sprint.
"It's frustrating for Duncan and ourselves that he's missing out on big games," the Warriors head coach said.
"However, with many more important fixtures coming up over the course of the season, it's very important that he gets himself right, and I know he'll be working hard with our medical team to return to the fray in due course."
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