Rennes beat Arsenal in Europa league Photograph:( Reuters )
Arsenal had never lost to French opposition away from home in 12 previous European games.
Chelsea outclassed Dynamo Kiev 3-0 in the first leg of their Europa League last-16 tie on Thursday but Arsenal face an uphill task to make the quarter-finals after slumping to a 3-1 defeat at French club Rennes.
Napoli, Dynamo Zagreb, Villarreal and Valencia will also take victories into next week’s second legs, while Sevilla v Slavia Prague and Eintracht Frankfurt v Inter Milan ended all square.
Chelsea were by far the better side at Stamford Bridge – they had eight shots on target to Kiev's none - but it was not until Callum Hudson-Odoi scored a third goal in stoppage time that the scoreline fully reflected their dominance.
Pedro put the home side ahead after 17 minutes when he played a one-two with Olivier Giroud and set them on the road to their eighth win in nine Europa League games this season.
Brazilian midfielder Willian made it two with a perfect free kick after 65 minutes before 18-year-old substitute Hudson-Odoi side-footed home.
Arsenal had never lost to French opposition away from home in 12 previous European games and they took an early lead when what looked like a cross from Alex Iwobi evaded everyone and sneaked in at the far post.
Playing in their change turquoise-green shirts, the English side controlled most of the first half but the match changed completely four minutes before halftime when Sokratis Papastathopoulos was sent off for a second bookable offence.
Rennes equalised from the resulting free kick when Benjamin Bourigeaud rifled home at the second attempt and they came out for the second half looking far more positive than the Londoners.
The French team went ahead 20 minutes into the second half when Mehdi Zeffane’s shot looped off defender Nacho Monreal into the net and Ismaila Sarr made it 3-1 two minutes from time when he powered home a header from a lovely curling left-wing cross.
First-half goals from Arkadiusz Milik and Fabian Ruiz, and an own goal by Jerome Onguene gave Napoli a 3-0 over Austrian champions Salzburg and extended their unbeaten home record in the competition to five matches.
Sevilla, who have won the Europa League three times, twice went ahead against Slavia Prague but were pegged back on both occasions in a pulsating 2-2 draw in Spain.
Wissam Ben Yedder put the home side ahead in the first minute and although Miroslav Stoch equalised with a deflected shot, Munir restored Sevilla's lead.
Alex Kral put the visitors level again six minutes before halftime when he turned a corner into the net.
Fellow Spaniards Villarreal had a happier evening in St Petersburg and will take a solid 3-1 lead over Zenit into the second leg at home.
Villarreal, third bottom of La Liga, took the lead after 33 minutes when Vicente Iborra headed home from a free kick but the home side took only two minutes to level thanks to Sardar Azmoun, whose quick thinking allowed him to stab home from close range.
The Spaniards, though, took control in the second half, with Gerard Moreno putting them 2-1 ahead after 64 minutes and Manu Morlanes added the third.
Valencia, UEFA Cup winners in 2004 and the third Spanish side left in the competition, beat Krasnodar 2-1 thanks to a first-half double from Rodrigo.
An improved second-half performance from the Russian side was rewarded with a goal by Swede Viktor Claesson.
Bruno Petkovic scored a penalty for Dinamo Zagreb to give them a 1-0 home win over Benfica while in the only game between two former winners of the UEFA Cup, Eintracht Frankfurt were held 0-0 at home by Inter Milan.
It was the first time Eintracht, who have won seven of their eight Europa League matches this season, failed to score.
The second legs take place next Thursday.