Arsenal put their pursuit of a place in the Premier League's top four back on track as they ended a run of three defeats with a crucial victory at Chelsea.
The Gunners had slipped from looking in pole position to secure a place in next season's Champions League but this win will provide renewed belief.
Eddie Nketiah was given the nod ahead of out-of-sorts Alexandre Lacazette in Arsenal's attack and he rewarded manager Mikel Arteta's faith when he took advantage of Andreas Christensen's header with a composed finish in the 13th minute.
It was the start of a chaotic first half as Timo Werner equalised with a deflected shot four minutes later before Emile Smith Rowe showed a real touch of class to beat Chelsea keeper Edouard Mendy from the edge of the area.