Mike Brown scored two tries for the Aviva Premiership Rugby outfit, while Nick Evans kicked 16 points, but their efforts could not stop Quins slumping to a 33-26 defeat at the Stoop.
They will have the opportunity to bounce back against Clermont Auvergne on Sunday and O’Shea is expecting much better.
“We have to man up and not feel sorry for ourselves,” the Quins director of rugby said. “We have to take the flak that will come our way and absolutely correctly come our way because we’ve earned that.
“There were some individuals out there who gave everything like Mike Brown, Nick Easter and Chris Robshaw, but it’s not a game of touch. At times it looked like that with some of the tries they scored. I thought we were terrible, we made so many basic errors. I’m furious.”
Meanwhile, Aviva Premiership table-toppers Saracens got their Heineken Cup campaign off to a winning start on Friday, edging to a 23-17 victory at Pro12 strugglers Connacht.
Elsewhere, London Wasps enjoyed a winning start to their European season, as debutant William Helu and Guy Thompsons grabbed hat-tricks in their 90-17 Amlin Challenge Cup win against Viadana.
And London Irish followed in Wasps’ footsteps in the Amlin Challenge Cup, as Jimmy Stevens, Myles Dorrian, Andrew Fenby and Sailosi Tagicakibau scored first-half tries against Italian outfit Cavalieri.
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