French club Monaco upset 10-man Barcelona by grinding out a 2-1 victory on Thursday in the Champions League, while a stunning David Raya double-save ensured Arsenal a goalless draw away to Europa League winners Atalanta.

Barca have started the season with a perfect record after five La Liga matches but, hindered by a red card in the 11th minute for Eric Garcia, fell to defeat on the French Riviera.

Maghnes Akliouche fired the French side into the lead five minutes after Garcia was dismissed for a last-man challenge on Takumi Minamino.

Teenage sensation Lamine Yamal equalised in the 28th minute with an arrowed shot after cutting in from the right onto his favoured left foot, but George Ilenikhena grabbed the winner for Monaco inside the final 20 minutes.

“After 10 minutes with the red card the game changed totally, but what I can see is really the positive thing,” Barcelona coach Hansi Flick told reporters.

“We tried to defend as a team and also attack as a team, and we had chances, but today they deserve the 2-1 (win), so we have to accept that.”

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In Italy, Arsenal goalkeeper Raya earned his side a point in a tough start to their campaign against Atalanta with a 0-0 draw.

A tight match was lit up six minutes after the interval when Mateo Retegui saw Raya plunge down to his right to keep out his penalty, after a foul by Thomas Partey on Ederson.

The ball rebounded up in the air and Retegui looked set to casually nod the dropping ball into the gaping net but the Spaniard sprang to his feet and hurled himself back across the goal-line to claw the ball to safety.

“It’s just a penalty and I was lucky to go the right way and save it,” Raya told TNT Sports.

“I was unlucky to give the rebound straight back to him but I was quick enough to get up and save it.”

A 90th-minute header by Jose Maria Gimenez sent Atletico Madrid coach Diego Simeone scuttling down the touchline in delight as his side edged visitors RB Leipzig 2-1.

Benjamin Sesko had put the German side in front just four minutes in, but Antoine Griezmann equalised just prior to the half-hour with a controlled finish from inside the penalty area.

The Frenchman then turned provider as he chipped a cross into the box, which Gimenez leapt highest to win at the back post and glance the ball back across Peter Gulacsi and into the Leipzig goal to spark wild celebrations in the Metropolitano Stadium.

“It’s amazing, to get a last-minute goal like this is always fantastic and it’s good to give the fans something to cheer about,” Atletico’s former Leipzig striker Alexander Sorloth told DAZN.

Bayer Leverkusen starlet Florian Wirtz enjoyed a dream Champions League debut as the Bundesliga champions thumped Dutch side Feyenoord 4-0 away from home.

The 21-year-old scored a brace either side of an Alex Grimaldo strike before an own goal by Feyenoord goalkeeper Timon Wellenreuther ensured Leverkusen had the points wrapped up by half-time.

“It may have looked pretty easy, but it’s really not,” Leverkusen coach Xabi Alonso told reporters.

“Overall it was a very serious, very efficient performance from us, but it’s never easy.” French side Brest made a winning start in their first-ever appearance in European competition by seeing off Austria’s Sturm Graz 2-1.

Playing at Brittany rivals Guingamp’s home ground as their own stadium does not meet UEFA standards, Brest took the lead midway through the first half through Hugo Magnetti.

An own-goal by Edimilson Fernandes on the stroke of half-time levelled matters but Abdallah Sima’s smart finish in the 56th minute was enough to divide the sides.

Benfica held on in Serbia against Red Star Belgrade to claim a 2-1 win courtesy of goals in the first half by Turkish duo Kerem Akturkoglu and Orkun Kokcu.

The second matchday of the Champions League league phase will take place on October 1 and 2 with Arsenal hosting Paris Saint-Germain, Bayern Munich travelling to Aston Villa and reigning champions Real Madrid visiting Lille.

Champions League Results

Benfica 2 (Akturkoglu 9, Kokcu 29) def. Red Star Belgrade 1 (Milson 86)

Bayer Leverkusen 4 (Wirtz 5, 36, Grimaldo 30, Wellenreuther 44-og) def. Feyenoord 0

Atalanta 0 drew Arsenal 0

Atletico Madrid 2 (Griezmann 28, Gimenez 90) def. RB Leipzig 1 (Sesko 4)

Monaco 2 (Akliouche 16, Ilenikhena 71) def. Barcelona 1 (Yamal 28)

Brest 2 (Magnetti 23, Sima 56) def. Sturm Graz 1 (Fernandes (45+1-og)