The fifth and penultimate round of pool matches in European Cup action this weekend throws up some mouth-watering clashes as teams go head-to-head to nail one of the eight spots in the knock-out phase from six pools. Defending champions Leinster need a win over Glasgow on Sunday to guarantee top spot in Pool 3. Saracens also host twice beaten Cup finalists Biarritz in a do-or-die game on Sunday, the English champions atop Pool 5 from the Basque club by two points and knowing that a bonus-point win would also leave them as pool winners. But the four other pools are all wide open, with a bevy of the top European clubs vying for a vaunted spot. "There's no bigger game for us," said Saracens centre Brad Barritt, who has just received a call-up into the England squad for this season's Six Nations. "We know we must win if we want to continue to the quarter-finals, so the focus is definitely on the match. "We know from playing them away that Biarritz are going to be a very tough side to face. They've got everything to play for and they've got some great players right across the park." In Saturday's matches, two-time champions Munster reached the quarter-finals for the 13th time with a battling 26-10 win over Castres to clinch a fifth victory in five Pool 1 matches this season, while Northampton, the 2000 champions, recovered from a 14-6 half-time deficit to beat Scarlets 29-17 to move into second place in the pool, eight points behind Munster. Four-time champions Toulouse clinched a four-try, bonus-point 24-3 win over Connacht which gave them a two-point at the top of Pool 6 over Harlequins who defeated Gloucester 20-14. In Pool 2, Cardiff Blues, playing their 100th match in the competition, beat London Irish, 22-15, in Reading with Welsh skipper Sam Warburton grabbing the only try of the game early in the second half. The win moved Cardiff to 17 points, the same as Edinburgh who had needed a last-minute drop goal from replacement fly-half Phil Godman to secure a 27-24 win over Racing Metro on Friday. Cardiff face Racing in their final match next weekend as they look to reach the knock-out stages for the first time since the 2008-09 season. In Pool 4, Clermont ran in 12 tries in a 82-0 rout of hapless Italian side Aironi to move to 16 points, three behind Ulster, who eliminated double-champions Leicester 41-7 on Friday. Clermont and Ulster will meet in France next weekend in the final round of matches, a game which will decide top spot in the section. In Pool 3, Montpellier defeated Bath 24-22.