Wasps edged by lacklustre Toulon
Error-strewn Toulon failed to convince but still stepped up their quest for a record-breaking third consecutive European title by edging past Wasps 32-18 at Stade Mayol.
The double-Heineken Cup champions and Top 14 league title-holders started strongly, stuttered - but still strode home, to set up a Champions Cup semi-final with Leinster.
Wasps' Tonga wing Will Helu pinched a second-half brace to give Toulon pause, but the reigning European kings clawed enough nous to ensure victory.
Toulon will take on three-time Heineken Cup winners Leinster at Marseille's Stade Velodrome in the last four, but they were sloppy in the extreme for the majority of the game.
Frederic Michalak was his unpredictable best with ball in hand, but for once the former France fly-half was also faultless from the tee.
The 32-year-old's flawless kicking return of 22 points effectively separated the sides and inched Toulon into the final four.
Mathieu Bastareaud struck early for the hosts, but Wasps refused to be cowed, and somehow found a foothold.
Dai Young's men can be proud of their European adventure, in their first top-tier knockout stage run since their 2007 Heineken Cup title.
Mourad Boudjellal showed his stern streak by threatening to return the Top 14 champions' Bouclier de Brennus trophy to the league's offices after last weekend's miserable 34-24 defeat to Toulouse.
The hosts struggled to appease their taskmaster owner, and that aim could perhaps account for a level of their sloppiness.
The fervent home support achieved its intimidation target immediately, Guy Thompson knocking on the first high ball of the match.
Toulon needed less than 10 minutes to take control, France centre Bastareaud barrelling home after a lineout drive.
Michalak added the extras for an ominous opening, but somehow Wasps summoned a scrum platform.
The visitors exploited an early set-piece edge to allow Lozowski to cut the deficit to four points from a penalty.
Toulon's enviable power allowed the hosts to grind their way through Wasps' line almost at will, Ali Williams and Bakkies Botha both making telling clean breaks.
Wasps countered with a smart backline scythe of their own, Elliot Daly stepping through traffic to send Rob Miller tearing away.
The former Sale full-back's attempted pass to Tom Varndell was batted away by Delon Armitage however, with the ex-London Irish man perhaps fortunate to escape punishment.
Toulon were quickly buccaneering again though, this time hooker Guilhem Guirado scampering away in midfield.
Wasps scragged the high-stepping front-rower deep in their own 22, only for Miller to receive a yellow card for killing the ball at the tackle.
Michalak posted two penalties to one from Lozowski as Wasps got to grips with Miller's sin-binning - and then Toulon started wasting chances by forcing the issue.
So desperate were the hosts to atone for that rare blip at Toulouse that every chance to move the ball wide was seized with troubling alacrity.
Michalak almost confused himself with a blindside switch that Varndell just about snuffed out, then Carl Hayman could not hold on after a bout of juggling.
Miller returned to restore Wasps' full complement, but parity in numbers did little to stymie the Toulon onslaught.
Michalak added his fourth and fifth penalties of a flawless kicking half as Toulon turned around 22-6 to the good.
Toulon botched another try-scoring chance at the top of the second half - and then gifted Wasps a route back into the contest.
Josua Tuisova slipped in midfield as Wasps ran a regulation backs move, and the Fijian wing's mistake handed Helu a straight run-in.
Replacement fly-half Andy Goode slotted the conversion, and suddenly Wasps trailed by nine points.
Even though Toulon still boasted a healthy cushion, Bernard Laporte's men conspired to become ever-more error-strewn.
So what ought to have been a regulation victory instead became a real scrap.
Toulon finally posted some second-half points when Michalak landed his sixth penalty with 12 minutes to play, a goal that eased fraying minds and tempers on the Cote d'Azur.
Just when Toulon expected to slide home undeterred though, up popped Helu again, tiptoeing to his and Wasps' second try.
Goode had the chance to cut the deficit to five points with six minutes to play, but dragged the tricky effort wide.
Wasps could still have pilfered a draw through a converted try - until Ali Williams trotted into the right corner.
Michalak added the conversion for good measure, finally killing off the contest with two minutes on the clock.