The France midfielder followed up to score after Andre Ayew's effort had been saved to close the gap on leaders Paris St Germain to six points.
The capital club can re-establish a nine-point advantage if they win their game in hand at struggling Evian tomorrow, though, with just 12 left to play for after that.
It was a fourth 1-0 win in five games for Marseille, and their 12th of the season - equalling PSG's Ligue 1 record.
The match ended on a sour note, though, with Lorient goalkeeper Fabien Audard and Ayew both sent off for clashing after the final whistle.
Elsewhere, Dennis Oliech's stoppage-time goal sealed a valuable win for Ajaccio
after they came from behind to beat Montpellier 2-1 in a game which saw both sides finish with 10 men.
The victory, which will have gone some way to help ease Ajaccio's relegation worries, came after Oliech headed the home side ahead with only seconds left on the clock after Andy Delorte had cancelled out Anthony Mounier's earlier strike for Montpellier.
It was a dramatic game which saw Ajaccio go close three times in the first half before defender Fousseni Diawara was shown a red card early in the second after he brought down Montpellier striker Souleymane Camara to concede a penalty.
Younes Belhanda missed the resulting spot-kick but Mounier gave Montpellier the lead soon after following a great counter-attacking move.
Montpellier defender Abdel El Kaoutari then hauled down Delorte inside the area and was shown red, with the Ajaccio substitute striker stepping up to shoot low into the left-hand corner and level the score before Oliech headed the winner with seconds remaining.
In the other games, Rennes claimed their first league win in 10 after they beat Brest 2-0.
First-half goals from Abdoulaye Doucoure and Victor Montano did the damage to keep Rennes in the top half of the table while Brest slipped nearer to Ligue 2.
They are now five points adrift of the safety line, a situation which would become even more bleak should Evian earn an unlikely result tomorrow against leaders Paris St Germain.
Bastia and Toulouse did little to set pulses racing as they played out a drab 0-0 stalemate that leaves both still mired in mid-table mediocrity.
With both sides seemingly clear of the battle to beat the drop and well short of European qualification, there was an end-of-term feel to proceedings with neither side firing on all cylinders.
The draw was at least sufficient for both sides to snap losing streaks, with Toulouse coming off three straight reverses and Bastia beaten in their last two before tonight.
Valenciennes and Nancy also played out a goalless draw as Nancy keeper Damien Gregorini earned his side a point with an excellent display at the Stade Du Hainaut.
Gregorini made a string of saves, most notably from Opa N'Guette midway through the second half, to claim a valuable point in the relegation battle.
Nancy, rock bottom for so much of this season, are now a point above the relegation zone with four games to play after a six-match unbeaten run.
Elsewhere, Reims edged away from the relegation zone following a goalless draw at Bordeaux.
Hubert Fournier's side enjoyed the best of the chances and Floyd Ayit saw a shot cleared off the line late on as they had to be content with a point.
It moves Reims four points clear of the bottom three with four games remaining.