A moment of genius from scrum half Danny Care was not enough to inspire Harlequins as they all but crashed out of the Heineken Cup after a 16-13 defeat to Clermont Auvergne.
The 27-year-old's reverse pass on the touch line midway through the first half - after collecting captain Chris Robshaw's chip - set Matt Hopper up to put his side7-3 up before two Nick Evans penalties made it 13-3 at half time.
But they could not withstand Clermont's second half onslaught as tries from Naipolioni Nalaga and Sitiveni Sivivatu and a late Brock James penalty booked the French side a place in the last eight.
O'Shea said: "We knew we'd be up against it at times and it would be the team that scrambled the most.
"The pitch was heavy going but we scrambled and stayed in it but we could not quite seal the deal when we had the chance.
"It is disappointment, but we'll get over it and get on with it."
Quins, who are out of the competition barring an extraordinary sequence of results in the final round of group games, can still secure a spot in the Amlin Cup, but will need to win at Scarlets next week.