In Istanbul, Galatasaray fell 1-0 to Union Saint-Gilloise, ending their three-match winning run.
Chelsea produced one of their strongest displays of the Champions League season with a 3-0 win over Barcelona on Tuesday, while Galatasaray, missing injured forward Victor Osimhen, slipped to a disappointing home loss that complicates their push for a top-eight finish.
Chelsea overpower 10-man Barcelona at Stamford Bridge
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Chelsea moved closer to securing qualification after a confident performance against Barcelona, who suffered their second defeat of the campaign.
After an early miss from Ferran Torres, Barcelona struggled to settle. Chelsea had two goals ruled out, but pressure eventually told when Jules Koundé turned the ball into his own net from a corner in the 27th minute.
Barcelona's task became more difficult just before halftime when Ronald Araújo received a second yellow card for a late challenge on Marc Cucurella. The hosts capitalised on the numerical advantage 10 minutes into the second half through Estevão, who drove into the box before finishing calmly.
Chelsea sealed the win in the 73rd minute when Enzo Fernández released Liam Delap for a simple tap-in. Although initially flagged offside, VAR confirmed the goal, giving Chelsea a deserved 3-0 victory.
The London club now move within reach of the top spots, while Barcelona remain under pressure going into the final matchday.
Osimhen missing as Galatasaray suffer shock home defeat
In Istanbul, Galatasaray fell 1-0 to Union Saint-Gilloise, ending their three-match winning run.
Nigerian striker Victor Osimhen, the Champions League's leading scorer, missed the game through injury, and his absence was evident as the hosts struggled to convert long spells of pressure.
The Belgian side grew in confidence and took the lead in the 57th minute when Promise David finished a flowing move after an assist from Adem Zorgane. Galatasaray hit the post and dominated possession but could not find a breakthrough. Their night worsened when young defender Arda Ünyay received a second yellow card in the closing minutes.
The defeat leaves Galatasaray vulnerable in the standings, with qualification still in the balance heading into Matchday 6.
Manchester City stumble, Leverkusen rise
Pep Guardiola's 100th Champions League match as Manchester City coach ended in frustration as his heavily rotated side lost 2-0 away to Bayer Leverkusen.
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Alejandro Grimaldo put the Germans in front with a low drive in the 23rd minute, and Patrik Schick doubled the lead early in the second half.
The result denied City the chance to move to the top of the table, with the upper positions unchanged going into Wednesday's fixtures.
Benfica claim first win, Ajax continue to struggle
José Mourinho's Benfica secured their first Champions League victory of the season with a 2-0 win over Ajax in Amsterdam. Samuel Dahl opened the scoring with a well-struck volley, and Leandro Barreiro added a late second.
Ajax remained at the bottom after losing all five of their matches in the competition and enduring a poor run across all competitions.
Scott McTominay was also on target as Napoli defeated Qarabag 2-0, on a night the club marked the fifth anniversary of Diego Maradona's passing.
