Undefeated Harlequins and Clermont can book European Cup quarter-final places this weekend with big-spending Toulon close to virtually wrapping up their spot in the last eight. English champions Harlequins, bidding to make the knockout stages for just the fifth time, already have 19 points from four Pool 3 wins and on Saturday tackle Connacht where just a losing bonus point will be enough to see them through. But they will also be fired up by the desire to grab a home tie in the quarter-finals ahead of their final pool clash next week, a tricky trip to Biarritz. In Pool 5, Clermont only need a home win over Exeter to book their place in the last eight for the third time in the last four seasons. Their double triumph over two-time defending champions Leinster means that the Irish side will probably need try bonus-point victories over the Scarlets and Exeter in their last two games to stay in the race to qualify as one of two best runners-up. Joe Schmidt\'s Leinster welcome rock-bottom Scarlets and will be boosted by the return of Lions trio Brian O\'Driscoll, Rob Kearney and Luke Fitzgerald. Kearney and Fitzgerald have yet to play in the European Cup this season but both featured for an hour in the 31-16 triumph over Edinburgh in the Celtic League last week while O\'Driscoll played the full 80 minutes. Toulon, the only other undefeated team after four rounds, host Cardiff on Saturday with a five-point lead in Pool 6 over Montpellier who go to struggling English side Sale. But the Top 14 leaders suffered a jolt to their confidence last weekend when they slumped to a 19-15 defeat to Racing Metro. That loss had Toulon president Mourad Boudjellal fretting over the strength of his squad despite huge investment in a wealth of overseas talent. \"When we are missing one or two important players, we are not the same team,\" said Boudjellal. Two-time winners Leicester and four-time champions Toulouse are locked in a battle of European war horses in Pool 2. Leicester have a one-point advantage over their French rivals, who are bidding to make the knockout stages for the 15th time. They meet at Leicester\'s Welford Road in the final round of group games next week. On Sunday, however, the Tigers go to Swansea to face the Ospreys while Toulouse welcome bottom-club Treviso who have just one point from four games. In Pool 1, Saracens are two points clear of Racing Metro ahead of their match against the French side which is taking place in Nantes. A win for Saracens would end Racing\'s hopes of automatic qualification while Munster, the 2006 and 2008 champions, will stay in contention if they beat pointless Edinburgh. Ulster, the 2012 runners-up, lead Pool 4, three points ahead of Castres, and meet Glasgow at Ravenhill on Friday. Ulster suffered their first defeat of the season when Northampton won 10-9 in Belfast before Christmas. From : AFP