Erling Haaland scored his 20th goal for Manchester City as his side swept Southampton aside to move top of the Premier League.
The 22-year-old Norway striker has taken only 13 games to reach that mark in all competitions, with struggling Saints the latest side to find out how hard it is to keep him or his team-mates quiet.
City attacked relentlessly from the start and Haaland was within inches of giving them an early lead when he hit the inside of the post after galloping clear.
Instead it was Joao Cancelo who put the home side ahead, running on to Phil Foden's pass and cutting past James Ward-Prowse before finding the bottom corner of the net.
Foden, who like Haaland scored a hat-trick here against Manchester United last weekend, got on the scoresheet himself soon afterwards with a dinked finish after Kevin de Bruyne found him in space in the box.
That put City in complete control at the break and they wrapped up the points at the start of the second half when Mahrez volleyed home a Rodri cross.
City manager Pep Guardiola later said: "The result is good, we play quite good. We struggled to break their high pressing. Last season we suffered a lot against them but today we were much better.
"Some players were not at their best but we create a lot of chances. We were solid. It was a good game.
"For a long time Phil Foden is playing really good. The impact from him is great.
"Erling Haaland had the chances again. He scored a brilliant goal. It's an incredible weapon for us, a big threat. I am so satisfied.
"We will see the result from Arsenal and Liverpool, always in Premier League there are good games.
"Being close to the top of the league is important going into the World Cup."