Paris - Two-time defending champions Leinster were left teetering on the edge of going out in the pool stage of this season's European Cup after being outplayed in a 28-21 defeat at home to French side Clermont on Saturday.
Clermont's victory - built round 23 points from France star Morgan Parra's boot - saw them move onto 18 points while Leinster are on 10 points, after grabbing a defensive bonus point right at the death when Fergus McFadden touched down.
It gave the record crowd for a pool match - just over 48,000 - something to console themselves with.
"We are very happy as every other time we have come here we have lost," said Parra.
"Our defence was the difference, which meant we got to control the ball."
His captain Aurelien Rougerie paid a handsome tribute to the France scrum-half.
"He was everything to do with this victory. It is down to him."
Exeter are a point behind Leinster - with two games remaining - as they secured a second successive win over Welsh side Scarlets, with a 30-20 win at home.
Clermont led 9-6 approaching the break when they landed a huge psychological blow as they scored a superb try.
Wesley Fofana burst over the line after Napolioni Nalaga had been brought down just short - Parra landed the conversion to give them a 16-6 lead at half-time.
Parra and Jonathan Sexton each converted a penalty early in the second-half.
However, the hosts' chances of getting back into the match got slimmer in the 50th minute when flanker Sean O'Brien was sin-binned for a dangerous challenge on Sitiveni Sivivatu and Parra landed the resulting penalty for 22-9.
Parra added another in a peerless display of kicking but the Irish side, at last showing some fire, saw Shane Jennings go over - for only their second try in this season's tournament - and Sexton added the conversion for 25-16.
Parra, though, added yet another three points leaving the hosts 10 minutes to recoup something from the match which they did when Sexton burst from the halfway line and fed McFadden, who may have secured what turns out to be a crucial bonus point.
Earlier on Saturday Ospreys restored some pride to Welsh club rugby with an impressive 17-6 victory over four-time European Cup winners Toulouse in their Pool 2 match.
The Ospreys, whose two wins in this season's competition are the only ones from 11 games Welsh sides have played in, scored the one try of the game through man of the match Eli Walker against a Toulouse side that totally under-performed.
Leicester went top of the pool after they eked out a come-from-behind 14-13 win over Treviso in Italy.
The English side, who travel to Ospreys in the next round of matches in January, lead Toulouse by a point with two games remaining while Ospreys are five points adrift of the pool leaders.
Leicester host Toulouse in what should be a thrilling final pool game.
Toulouse general manager Guy Noves conceded that his side had not deserved to win.
"We knew that we wouldn't earn our spot in the knockout stages even if we won here and similarly we knew if we lost we wouldn't be eliminated," he said.
"But I'm disappointed by our performance. I was expecting something else. There are a lot of things to be said to the team about this match, that is for sure."
The key moment came with Toulouse's second yellow card in the game close on the hour mark when experienced flanker Jean Bouilhou was sin-binned for a high tackle on the outstanding 20-year-old wing Walker.
Walker made them pay double for that as he was released on the left wing and evaded a dreadful attempt at a tackle by opposite number Yoann Huget to touch down and Toulouse never looked like recovering the ground.
Ospreys (WAL) 17 Toulouse (FRA) 6
Treviso (ITA) 13 Leicester (ENG) 14
Harlequins (ENG) 53 Zebre (ITA) 5
Ulster (IRL) 9 Northampton (ENG) 10
Exeter (ENG) 30 Scarlets (WAL) 20
Leinster (IRL) 21 Clermont (FRA) 28
Montpellier (FRA) 34 Cardiff Blues (WAL) 21
Edinburgh (SCO) 3 Racing Metro (FRA) 15
Biarritz (FRA) 17 Connacht (IRL) 0
Saracens (ENG) v Munster (IRL) (1500)
Castres (FRA) v Glasgow (SCO) (1245)
Toulon (FRA) v Sale (ENG) (1500)