Harlequins director of rugby Conor O’Shea insists it is win or bust as his side goes in search of a place in the European Challenge Cup knock-out stages.

Quins thumped Italian’s I Cavalieri Estra 48-16 on Saturday, but need to beat French side Bayonne to be certain of a home quarter-final draw in the next round.

A defeat at the Stoop - without securing a losing bonus point - would see O’Shea’s men elliminated and the Irishman believes his men must take an ‘all or or nothing’ approach to the clash.

“It is do or die for us this week. If they get four points and we get nothing we are out,” he said.

“It is already a knock-out stage in our mind and that is the way we are approaching it.

”We are in good form and we want to sustain the momentum we have created over the last few weeks.

“But we know it is going to be tough. They have beaten Castres, Agen and Toulon in their last five games, so it is going to be a massive challenge and an exciting game.”

Winger Sam Smith bagged a second half-brace - adding to scores from Maurice Fa’asavalu, Danny Care, Tom Casson and Karl Dickson - reflecting the strength in depth in O’Shea’s squad.

“One or two were rested at the weekend, but we keep the core of our team playing week in, week out and demand people take their chance when they step up,” said the Stoop chief.

“Sam is a talented player and he took his chance well. It is a long season and we are battling on three fronts, so you need that sort of attitude.”

Quins have lost just twice in their last 11 games - since a 6-6 draw with Bath - and O’Shea believes that is a sign his men have put the frustrations of 2010 behind them.

“All the way through we have been happy with what we have been producing, but without getting results,” he said of the side’s turnaround in fortunes.

“The players have been working incredibly hard and we just want to make sure winning becomes a habit now.”

Quins’ next three games: Jan 22 Bayonne (European Challenge Cup, h), 30 Lonon Wasps (LV= Cup, a, UAE), Feb 6 Cardiff Blues (LV= Cup, h).