Scotland scrumhalf Greig Laidlaw scored 20 points to help Clermont return to the number one spot in the Top 14 after thumping Bordeaux-Begles 40-15.
The home side fell to second in the table after defeat to champions Castres in late January but Laidlaw's perfect performance from the boot saw them back to the top as the visitors had winger Blair Connor sent from the field for dangerous play.
Laidlaw was playing for his club in a weekend without Six Nations games. He is set to face France in Paris next Saturday in the competition.
Joe Worsley's outfit started the game the strongest as winger O'Connor crossed after two minutes after Clermont's Peter Betham failed to deal with a grubber kick.
Laidlaw claimed his first points of the match as he slotted a penalty goal on 11 minutes. He doubled his tally and put the hosts into the lead five minutes later with another effort from his trusted right foot.
Clermont extended their lead as back-rower Alexandre Fischer opened his account in his first start for Franck Azema's side and Laidlaw added the extras.
Bordeaux's former Clermont fly-half Brock James slotted a penalty on 39 minutes before Laidlaw regained the eight-point advantage with a further three points seconds before the half-time whistle.
Laidlaw made it four successful kicks from as many attempts on 45 minutes with another penalty goal.
Less than 10 minutes later Bordeaux-Begles were down to 14 men as Connor was shown a red card.
Attempting to clear out Clermont's Nick Abendanon at a ruck he picked up the England fullback and clumsily left him to fall onto the ground.
Azema's outfit made the one-man advantage count shortly after as Fiji's Peceli Yato touched down for an 11th time this campaign thanks to a delicate Tim Nanai-Williams chip kick to give them a 26-8 lead with a quarter of the game to play.
An attempted comeback from the visitors was inspired by former All Blacks center Seta Tamanivalu who set up Fiji's Semi Radradra for a try.
But the home side secured a return to the top of the table as Paul Jedrasiak crossed twice in the final 15 minutes.
Elsewhere on Saturday Montpellier play winless Perpignan, Stade Francais welcome Lyon and Pau face Castres before Toulon head to Agen.
On Sunday Grenoble host La Rochelle and Toulouse can regain top spot when they travel to Racing 92 LIVE on FloRugby.
© Agence France-Presse