Times are changing at Stamford Bridge. Even Arsenal, who once dreaded a trip to this corner of west London, have lost the fear. There is nobody of Didier Drogba’s ilk to bully their defenders into submission these days and, as a measure of how readily Mikel Arteta’s players accepted the challenge of breathing life back into their Champions League challenge, nothing summed it up more than Bukayo Saka converting the penalty that finally dashed Chelsea’s hopes of stealing a point. It was a moment of huge significance for Saka, who had not taken a spot-kick since missing the decisive one when England lost to Italy in the Euro 2020 final. There were no nerves from Arsenal’s brilliant young winger. Saka was full of belief after tormenting Chelsea’s faltering defence and his steel under pressure meant that Arsenal, who had a point to prove after three successive defeats, could celebrate going level with fourth-placed Tottenham with six games left. The race for fourth is alive. Out of nowhere, Arsenal have momentum again. They have another opportunity to kick on when they host Manchester United on Saturday and, for all that their youthful inexperience threatens to hold them back, there is every chance they will come to look back on this victory over Chelsea as a defining moment in their development. This was a vibrant performance, made all the more impressive by the fact Arsenal did it without Thomas Partey and Kieran Tierney. There was an excellent display in attack from Eddie Nketiah, who grabbed his first league strikes of the season. Emile Smith Rowe took his goal beautifully. Saka never stopped running and Granit Xhaka was strong alongside Mohamed Elneny in central midfield, where Chelsea’s lack of urgency left them open to Arsenal’s counterattacks. Chelsea, who have conceded 11 in their last three home games, could have no complaints. For the second time in four matches Thomas Tuchel withdrew Andreas Christensen at half-time but the change had no effect. Chelsea, who are only five points above Spurs, were far too unfocused and it spoke volumes that Tuchel was reduced to criticising the pitch when he analysed the error from Christensen that led to Nketiah opening the scoring. All is not well at Chelsea. They had to endure Arsenal’s fans laughing at the 10,000 empty seats in the home areas and the night ended with César Azpilicueta, Tuchel’s captain, remonstrating with one of his own supporters. Tempers were frayed. The home crowd would also vent their frustration at Romelu Lukaku when the £97.5m striker was replaced after 60 sluggish minutes. There were a few boos for Lukaku and it is difficult to see much of a future for him at Chelsea. Arsenal’s prospects looked brighter. They wore black armbands in remembrance of their former chief scout Steve Rowley who passed away at the age of 63, and were ahead after 13 minutes. The goal summed up Chelsea’s difficulties after resting Thiago Silva and starting Malang Sarr in place of the injured Antonio Rüdiger. A punt from Nuno Tavares had Christensen running towards his own goal and flailing under pressure from Nketiah, who was eager to impress after starting instead of Alexandre Lacazette. Christensen, who is expected to join Barcelona on a free, was all over the place. The centre-back’s backpass was underhit and Nketiah, who is out of contract at the end of the season, ran on to beat Édouard Mendy with a cool finish. Arsenal soon proceeded to hand out a few gifts of their own. Ruben Loftus-Cheek quickly won possession high up the pitch and Timo Werner equalised after letting fly with a shot that spun past Aaron Ramsdale thanks to a heavy deflection off Xhaka. Yet the equaliser did not alter the pattern of the game. There was danger every time Saka ran at Sarr and Marcos Alonso on the right, and Chelsea were soon behind again. Xhaka rescued Rob Holding from a mess of his own making before calmly bringing the ball out from the back, Saka and Martin Ødegaard combined well and Smith Rowe fired past Mendy. Back came Chelsea, though, equalising again on 32 minutes. This time Ben White was at fault when he gave the ball away to Mason Mount and appealed for a free-kick. Jon Moss was not interested in White’s complaints and Mount crossed for Azpilicueta to peel past Tavares and prod the ball beyond Ramsdale. Yet Chelsea were still a mess. After 57 minutes Azpilicueta misplaced a pass and Tavares attacked. The left wing-back found Nketiah and, when Silva, Sarr and N’Golo Kanté failed to clear, the striker prodded the ball past Mendy. It was another self-inflicted wound. Tuchel tried to respond, replacing Lukaku with Kai Havertz, but there was no way back. Arsenal pushed on the break and the points were theirs when Azpilicueta conceded a penalty for fouling Saka, who finished confidently. Arsenal sensed a power shift.