Monaco were far from their best against a Lorient side buoyed by the arrival of Bernard Casoni as coach
Radamel Falcao lashed home seconds after coming on as Monaco usurped Nice at the top of Ligue 1 with a 3-0 away win at bottom side Lorient on Friday.
Monaco, who face Tottenham Hotspur at Stade Louis II on Tuesday in the Champions League, go provisionally top on goal difference with Nice at Saint-Etienne on Sunday.
Champions Paris Saint-Germain, the third team in what looks increasingly like a three-horse race for the French title, host Nantes on Saturday. They are on 26 points, three behind Monaco and Nice.
Lyon climbed to fourth, on 22 points, with a 1-0 win in Lille.
Monaco, who started revitalised striker Falcao on the bench -- presumably with Tottenham in mind -- were far from their best against a Lorient side buoyed by the arrival of journeyman Bernard Casoni as coach.
The scoreline flattered the visitors, whose coach Leonardo Jardim said afterwards: "In the first-half we had three or four good situations in which we might have scored.
"In the second period we were superior to them, especially in the last 30 minutes. We scored three times and I think deserved the win.
"I had told my players that with a change of coach, normally the opposing team will work hard at the start of the match, trying to squeeze, trying to win duels, but that perhaps they would not be able to do that for 90 minutes."
Monaco made a fast start and should have been ahead after 40 seconds but forward Valere Germain headed wastefully over when unmarked.
Soon after Lorient ought to have gone ahead through Steven Moreira, but he shot wide with only goalkeeper Danijel Subasic to beat, with Monaco looking frail at the back.
Just three minutes after the break Monaco went a whisker from taking the lead when midfielder Thomas Lemar drove unchallenged from the half-way line and let fly from outside the box, only for his shot to veer away and strike the foot of the post before pinging away to safety.
The rain was falling heavily now and the game threatened to become a damp squib with both sides failing to get to grips with the deteriorating conditions in northwestern France.
Jardim had seen enough and sent on Falcao on 63 minutes.
Barely a minute later the Colombian -- who suffered successive poor spells at Manchester United and then Chelsea, before returning to France -- scored.
The ball bounced off a Lorient defender and fell into his path inside the box for him to smash home first time for his sixth goal in his last five games and help further erase the bitter memories of his ill-fated experiment in the Premier League.
Three minutes later the visitors went 2-0 ahead, Lemar bending the ball with his left foot up and over the wall and into the far corner with a beautiful free-kick.
Three minutes into injury time it was 3-0 as another substitute, Gabriel Boschilia, hit a free-kick that ricocheted off the Lorient wall and looped in.
Lorient remain rooted to the bottom of Ligue 1 with seven points from 13 games.