Arsenal continues their new-found good run as goals from Nicolas Pepe, Bukayo Saka and Alexandre Lacazette gave the Gunners their fifth win in six league games.
Stuart Armstrong’s finish from a clever James Ward-Prowse corner put Saints ahead (4), but Pepe answered some critics with a low finish inside the box from Granit Xhaka’s through ball (8).
Saka got Arsenal’s second just before the break, rounding Alex McCarthy after Lacazette’s threaded ball (39), and Saka turned provider for Lacazette in the second half for a well-constructed third (72).
Arsenal are now only five points off the top four, while Saints are a point behind in 11th.
Manchester City reached the summit of the Premier League for the first time this season after an irresistible performance saw them sweep past West Brom 5-0.
In what was arguably one of the most complete 90 minute performances of any team in the Premier League this season, City took an early lead when Ilkay Gundogan fired home (6) from 20 yards after a wonderful pass from Joao Cancelo.
The full-back went from supplier to finisher when doubling the lead via a brilliant curling effort from the edge of the area (20). The goal was initially ruled out for offside in the build-up but VAR overturned the decision after referee Chris Kavanagh had allowed play to continue despite the assistant referee raising the flag.
Gundogan – playing in a false nine position in the absence of Kevin De Bruyne – grabbed his seventh goal of the season with another tidy finish (30) before Riyad Mahrez capped a sensational team first-half performance with an outstanding solo effort (45). Raheem Sterling got in on the act in the second half (57) as City continued their winning streak in all competitions, which is now at 11 games.