Kylian Mbappe made his return from a post-World Cup holiday but Paris Saint-Germain went down 1-0 away to Rennes in Ligue 1 on Sunday, a result which leaves them just three points clear at the top of the table halfway through the season.
Rennes captain Hamari Traore scored the game's only goal in the 65th minute in the rain in Brittany to condemn PSG to a second successive away league loss after they went down 3-1 at second-placed Lens on New Year's Day, AFP said.
Prior to that they had gone unbeaten through their first 23 matches this season in all competitions and this latest setback gives their rivals hope in the title race.
"I am disappointed with our performance because we conceded too many chances and created nothing," said PSG coach Christophe Galtier, who complained of a "total absence of a presence in the penalty box" after opting to leave Mbappe on the bench at kick-off.
This was the first time that Mbappe, Lionel Messi and Neymar had appeared on the pitch together since PSG's superstar attacking trio returned from the World Cup.
Messi had been afforded an extended holiday after guiding Argentina to glory in Doha and scored on his return in a 2-0 win against Angers in midweek.
Mbappe, scorer of a hat-trick for France in the World Cup final as they lost on penalties to Argentina, had played in his club's first two games after the tournament before missing their last two as he took a holiday in New York with teammate Achraf Hakimi.
He was expected to start on Sunday but instead began on the bench as the 20-year-old Hugo Ekitike played in front of Messi and Neymar.
Without their leading scorer PSG were blunt up front and Rennes goalkeeper Steve Mandanda did not have a save of note to make until he kept out a Danilo Pereira header three minutes into the second half.
Mbappe replaced Ekitike in the 56th minute and did so to applause from the home fans.
Yet Rennes went ahead soon after as their Malian right-back Traore swept in a cutback from Adrien Truffert, and Mbappe -- making his 200th Ligue 1 appearance -- then squandered a chance to equalise when he burst through on goal but blazed over with just the goalkeeper to beat.
- Neymar and Messi struggle -
With Neymar again ineffective and Messi not having the expected impact, it was Juan Bernat who came closest to equalising for PSG with a shot that was tipped over by Mandanda.
Galtier will hope his attacking trio can rediscover their early-season form quickly with a Champions League last-16 showdown with Bayern Munich now just a month away.
"For eight weeks the squad has been scattered about all over the place, with players learning different ways of playing with their national teams," said Galtier when asked if he was worried about his side's current form.
"We had two training sessions this week in which everyone worked together. We will need time and we will have time to work together and get back to playing the same direct style as before."
Rennes, who recently lost top scorer Martin Terrier for the rest of the season with a serious knee injury, have now won nine successive home league games.
They are fifth in the table, behind Monaco in fourth only on goals scored after the principality side crushed Ajaccio 7-1 earlier in the day.
Wissam Ben Yedder scored a hat-trick in Monaco's win, while Canada's Jonathan David netted twice as Lille crushed Troyes 5-1 to sit sixth.
Lens are PSG's closest challengers after beating Auxerre 1-0 on Saturday for their 10th consecutive home win.
Marseille are third, two points behind Lens and five clear of both Monaco and Rennes, after defeating Lorient 3-1 on Saturday.
