Thomas Tuchel warned Timo Werner he must keep improving after the Chelsea striker's first Premier League goal since April helped seal a 3-1 win against 10-man Southampton on Saturday.

Werner saved Chelsea from a frustrating end to a difficult week when he netted six minutes from full-time at Stamford Bridge.

Tuchel's side had been pegged back to 1-1 after James Ward-Prowse's second-half penalty cancelled out Trevoh Chalobah's early opener.

Ward-Prowse was sent off with 14 minutes left for a nasty lunge on Jorginho and Chelsea laid seige to the Southampton goal before Werner slotted home from Cesar Azpilicueta's cross.

Ben Chilwell's last-minute goal wrapped up the points as Chelsea moved top of the Premier League, two points ahead of second-placed Liverpool, who host Manchester City on Sunday.

"We are all relieved, him and me and the whole club. Every time he scores we have the feeling there is a VAR decision to take it away from him, there have been a lot of very narrow decisions," Tuchel said.

It was a much-needed victory for Chelsea after successive defeats against City and Juventus.

After a troubled first season at Chelsea, it was a rare upbeat moment for Werner, whose relief was clear as he celebrated wildly after scoring and then smiled and joked with fans while conducting pitchside interviews.

The former RB Leipzig star has been forced to play second fiddle to Chelsea's club record signing Romelu Lukaku since the start of this season, sparking reports Tuchel might be willing to offload him.

For a player who has had a remarkable 16 goals disallowed since he joined Chelsea, Werner will surely benefit from the jolt of confidence that will follow his second club goal of the season.

But Blues boss Tuchel has no intention of letting the 25-year-old relax after his match-winning heroics.

"It was very important goal for us to secure the win. And on the other hand he was there when he needed to be," he added.

"We're happy and relieved that he scored. He has to keep on going and a lot of things to improve."

Tuchel was rewarded for making five changes to the team that lost 1-0 at Juventus on Wednesday.

Chalobah, Chilwell and Ruben Loftus-Cheek all added energy and enthusiasm to a Chelsea team that had looked stale in their previous two games.

"They can help us because they have this kind of totally positive spirit and they don't feel the pressure. Of course we lost the last two games and we felt something was lacking," Tuchel said.

Kai Havertz and Hakim Ziyech were two of the victims of Tuchel's cull and the manager admitted both players had experienced a dip in form.

"We always try our best to bring the players in the best shape, but after some chances we have to admit that Kai and Hakim are not in their best moment," Tuchel said.

"It is not even their fault. They lost a bit of belief or confidence. We will not stop boosting them, we are not angry with them and there are no major concerns.

"But we have to pay attention to actual form and we need to win the games. At a club like Chelsea you need to be sharp every few days and fight for your place."