Marseille kept the Ligue 1 title race alive for another week as they claimed a 2-1 win over Bastia on Saturday night, while Lille slipped to a 4-2 defeat against Toulouse.
OM's victory means Paris Saint-Germain cannot officially win the title on Sunday when they face Valenciennes, but a win will put the Parisiens nine points clear with three games remaining, with Carlo Ancelotti's men boasting a vastly superior goal difference.
Andre-Pierre Gignac gave Marseille the lead in the first half, but Florian Thauvin equalised within a minute of the start of the second.
But with nine minutes to go Gignac earned his side victory, with defeat leaving Bastia in mid-table.
Lille's bid for a top-four finish suffered a blow as they suffered a 4-2 defeat at the hands of Toulouse.
Lille had not lost to Toulouse in their last 10 league encounters but that run came to an end at the Municipal Stadium as they slipped two points behind fourth-placed St Etienne.
Ben Yedder and Etienne Didot put improving Toulouse 2-0 up in the first half but Lille hit back to draw level just after half-time through goals from Marko Basa and Salomon Kalou.
The visitors could not build on that fightback, though, and Toulouse claimed the win thanks to efforts from Daniel Braathen and Eden Ben Basat.
At the other end of the table Brest dropped to the bottom of the league following a 2-1 loss at Montpellier.
Marco Estrada opened the scoring for the home side but Florian Raspentino quickly equalised before Souleymane Camara's second-half penalty handed Montpellier victory.
Brest, who have 29 points, are now six adrift of 17th-placed Nancy, who face Lyon tomorrow.
Troyes leapfrogged Brest in the table as they claimed a vital 1-0 win at home against Evian.
Jean-Christophe Bahebeck's goal four minutes after coming on earned the victory which leaves the hosts three points behind their opponents, who occupy the final relegation place, and four from safety.
Sloan Privat's first-half goal allowed Sochaux to register what could prove to be a vital win in the battle to avoid the drop.
The striker scored with 30 minutes on the clock and, with Lorient unable to respond, Sochaux moved out of the drop-zone and on to 37 points.
Reims and Ajaccio both missed the chance to pull further away from the relegation zone after they played out a 1-1 draw at the Stade Auguste Delaune II.
Adrian Mutu scored the opening goal for Ajaccio in the 25th minute, but the scores were level at half-time, which is how they remained, thanks to Aissa Mandi's headed equaliser.
Both teams are now five points clear of 18th-placed Evian.
O'Connor kept his cool to cancel out Massimo Luongo's 70th minute-opener - his thumping finish with 90 seconds to go setting the tie up perfectly for the second leg at Griffin Park on Monday.
It was rough luck for Tottenham loanee Luongo, who went from hero to villain as he made the crucial foul at the end of Brentford's best move of the night.
And given the penalty furore that surrounded the Bees' 1-0 defeat at Doncaster last Saturday - they missed one to lose an automatic promotion spot - O'Connor's cool head was even more impressive.
"Kevin is excellent," said Rosler. "He had not played for a long time but stepped up to the plate. It was a difficult situation for him as he was not playing many matches, but in all the games he looks very solid and does a great job.
"Obviously, in the end, he used all his experience and skills to convert the penalty and I'm very happy for him."
The German manager added: "The tie is wide open and I said before the game, we must make sure it was.
"To get a draw after all the circumstances of last week was a very good result.
"It was a difficult game with not much between the two teams. In the first half they pushed us back but we had the best chance.
"After seeing our games this season against Swindon, every time we've played them in a 4-4-2 and we've played well, that was the main reason we started that way, to match them up."
Kevin O'Connor's injury-time penalty cancelled out Massimo Luongo's 70th- minute opener for the Robins - his thumping finish with 90 seconds to go setting the tie up perfectly for the second leg at Griffin Park on Monday.
It was rough luck for Tottenham loanee Luongo, who went from hero to villain as he made the crucial foul at the end of Brentford's best move of the night.
MacDonald said: "The timing of the goal is obviously disappointing but it is 1-1 and we are both in the tie.
"I thought the conditions were difficult for both teams. No team really handled it in the way they'd have liked to.
"I think both teams were nervous as well as it was a big game. At half-time we felt we could do better as there wasn't really enough chances.
"I didn't think we passed it as much as we usually do, we got ourselves in good positions but didn't make enough good chances.
"The timing of the goal is tough to a certain extent and they are disappointed in there but we are evenly matched, it is a one-off game and it will be about who recovers quickest."
