Harlequins director of rugby Conor O'Shea admitted that the Scarlets were "a delight" to play against following their 22-20 win.
Ben Botica's late penalty sealed victory for Harlequins and ensured them of a place in the Challenge Cup quarter-finals away to Stade Franšais.
The fixture was an entertaining affair despite difficult conditions for both sides, with O'Shea offering praise for referee Jerome Garces.
Both teams scored three tries each, with Mike Brown, Ollie Lindsay-Hague and Karl Dickson going over for Quins.
"It was harem-scarem out there," said O'Shea.
"It is a delight to play against a team like the Scarlets, it really is. Both teams tried to play in a way that should be lauded.
"I thought we controlled the last six minutes of the game brilliantly. I am baffled that we didn't get more penalties at different times, but I thought the referee, overall, did a really good job.
"Given the conditions, I thought it was an incredible game.
"I said to the guys that, mentally, to come back from the disappointment of last weekend when we had the opportunity to beat Clermont Auvergne, I don't think you should underestimate how much it took for the group to come down here and finish off.
"To finish as one of the best runners-up in such a tough pool is a real credit to the guys.
"I think there were loads of pools of death in the Heineken Cup this season. We've won two away games, and I am delighted that we are through.
"We are now going to play against Stade Francais away, and the juices will really flow for something like that.
"I think it has made a big difference to the Amlin tournament with (three) Heineken teams coming into it. Stade Francais versus Quins is a pretty good game."