The Warriors, now second, missed the chance to put breathing space between themselves and the rest following the 21-10 reversal at the Liberty Stadium.
But with Ulster set to visit Scotstoun on Saturday, Townsend knows Glasgow's destiny is in their own hands.
"We really want to be at Scotstoun for the semis and we have the chance to make that happen by beating Ulster next weekend," Townsend told the Daily Record. "It will be a huge match and my guys are good enough to get that win."
The game against Ospreys hinged on a clinical 20-minute spell after half-time which secured the all-important win for the Welsh side with tries from Ben John and Rhys Webb putting the game out of reach.
A late try from Chris Fusaro couldn't prevent the Ospreys from picking up their fifth win on the trot and replacing Glasgow at the top of the GUINNESS PRO12 standings.
Townsend added: "We knew we would have to perform to our absolute best against the Ospreys and we didn't do that."
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