Marseille piled the pressure on their former coach Marcelo Bielsa after a 1-0 win at Lille on Sunday left the Argentinians side stuck in the Ligue 1 relegation zone.
Midfielder Morgan Sanson grabbed the only goal of the game in just the fifth minute at the Stade Pierre-Mauroy and Rudi Garcia's visitors held on to close out the victory.
OM moved up to fourth in the French top flight, eight points behind arch-rivals and league leaders Paris Saint-Germain, while Bielsa's Lille remain second-bottom and four points from safety.
The 62-year-old joined at the end of last season, and after a raft of new signings, expectations were high at Lille ahead of the campaign.
But they have yet to win in the league since the opening day of the season and are in danger of being relegated for the first time since being promoted in 2000.
Former Montpellier midfielder Sanson, 23, delivered the killer blow on Sunday as he took advantage of some static home defending to slot in Florian Thauvin's low free-kick.
Lille plugged away but failed to create enough clear-cut chances, with Ezequiel Ponce firing into the side netting deep into injury-time.
Earlier on Sunday, Lyon captain Nabil Fekir scored a fine first-half brace to lift his side to third after a 2-0 defeat of rock-bottom Metz.
The 24-year-old France international Fekir has scored nine goals already this season, spearheading the Lyon attack after the departure to Arsenal of prolific striker Alexandre Lacazette.
It was a fourth straight win for a confident looking side who host Everton in the Europa League midweek before a trip to their bitter regional rivals Saint-Etienne next weekend.
Sunday's win leaves Lyon on 22 points from 11 games, just three points behind defending champions Monaco and seven adrift of leaders Paris Saint-Germain.
The series of wins is also promising for under-fire coach Bruno Genesio, on whom fans appeared to turn after a 2-0 loss to PSG in September was followed by successive 3-3 draws.
"It's Everton next and the right result will see us qualify with two games to spare, so we want to get a good start," Genesio said of Thursday's Europa League date.
Fekir scored two and made a third two weeks ago as Lyon edged Monaco 3-2 at home and his emergence this season brings fresh hope to a club who last won the French league in 2008 after a decade of dominance.
"He has been decisive every time he has played in terms of goals and assists," Genesio said of Fekir.
"He has risen to his new role as captain and is performing at an international level."
Metz meanwhile were the first Ligue 1 club to fire their coach as Philippe Hinschberger made way for Frederic Hantz this week, but the club appear doomed with just three points from 11 games so far.
Monaco shrugged off the absence of leading scorer Radamel Falcao on Saturday as they eased to a 2-0 victory away at Bordeaux while Claudio Ranieri's Nantes went down to a rare defeat.
PSG, without the suspended Neymar, had maintained their unbeaten start to the campaign by brushing aside Nice 3-0 on Friday thanks to a brace from Edinson Cavani and a Dante own goal.