Munster might not be as mighty a threat in Europe as they were in an eight-year period when they reached four finals and won the trophy twice but they remain formidable opponents who have the knack of winning on the road.
No other team has won more away Heineken Cup quarter-finals than the Irish club and all the European experience will be in the visitors' corner.
Tournament points record scorer Ronan O'Gara will line up for his 109th Heineken Cup appearance looking to add to his 1,342 points and Donncha O'Callaghan his 88th while a fit again Paul O'Connell will be hoping to crown his 67th outing with a win in front of watching British & Irish Lions head coach Warren Gatland.
Gatland will complete his five-match round of European matches at the Stoop when he will be running the rule over O'Connell and many others besides ahead of his Lions squad announcement on 30 April.
England skipper Chris Robshaw will be out to make up for the disappointment of missing out on a Grand slam with his country by carrying his club one step nearer to a first Heineken Cup final.
The battle of the boots could be vital with O'Gara taking on home favourite and former All Black Nick Evans.
Harlequins were the No 1 ranked team after winning all six of their Pool matches but they will need to rediscover that form when it really matters if they are to take the next step on the Heineken Cup ladder to glory.
• Harlequins are the top points scorers in the Heineken Cup this season averaging 41 per game in the pool stage and scoring 28 tries in total.
• Harlequins enjoyed the biggest share of possession of all clubs in the pool stage, spending an average of 17m 55s per game with the ball, more than any other side.
• Munster back row, Peter O'Mahony, has made 70 carries so far - only two other players have made more.
• Since the 1998/99 season, Munster have failed to reach the quarter-finals of the tournament just once (2010/11). They have won nine of those 13 quarter-finals.
• Munster have won two thirds of their matches against English opposition in the tournament. They have suffered just 13 losses in 38 clashes with English clubs.