Timo Werner and Kai Havertz have struggled at Chelsea as they have yet to adapt to the different styles in the Premier League, according to Gus Poyet.

The Germany internationals moved to Stamford Bridge before the start of the season as part of a massive squad overhaul costing upwards of £222million.

Neither player has found top form in England, though, as Chelsea's run of two wins in eight league games saw Frank Lampard sacked as head coach and replaced by Thomas Tuchel.

Werner has nine goals and five assists in 28 games in all competitions this season, with only Tammy Abraham (11 goals and four assists) registering more direct goal involvements for the club. However, the former RB Leipzig star has scored just once in his previous 10 appearances, in a 4-0 FA Cup victory over League Two Morecambe.

Havertz, with five goals and five assists, is the only other Chelsea player to have recorded at least 10 goal involvements in 2020-21, but the reported £72m arrival from Bayer Leverkusen has been outshone in midfield this term by Mason Mount.

Former Leverkusen coach Tayfun Korkut told Sky Sports that Havertz "will probably never be the darling of the supporters because he is not someone who fights", although he insisted the 21-year-old should be given time to show his true quality.

Poyet, who spent four successful years at Chelsea, thinks the early "adrenaline" Havertz and Werner had after their transfers has worn off and that the differing approaches by opposition teams in England is posing them problems.

"I think at the beginning [of the season] it was decent [for Chelsea]," he told Stats Perform News. "I think when you have new players, the adrenaline of these players is incredible. They bring something special to the club, but then to maintain that, especially for young players, is very, very difficult.

"So, there is a period of adrenaline, in which you're going to give a lot. There is a period of adaptation and then there is English football, which even if you think that you know, I promise you, you don't until you are on the pitch every weekend, because every game is a different story, every game is a different challenge.

"Today, you play against a team that they're going to keep the ball, and tomorrow you're going to get a team that is going to play long ball and you're going to have to defend 100 balls in the box. And then the next day, somebody's playing on the break, and the next day somebody plays the same system as you, and then you change and they change. Every game is a different challenge.

"I think it's been tough especially for the youngest ones, especially for [Kai] Havertz and [Timo] Werner. Because you know they're playing now in a low moment and, normally it happens unfortunately for us, the decision to bring something different is by changing the manager."