Bayer Leverkusen's sporting director, Simon Rolfes announced that Kai Havertz has all the characters to be "world-class" but just needs time to fit in at Chelsea.
spent £72million (€80m) to get the Germany international from Leverkusen in September.
The 21-year-old was one of many big-money signings, with compatriot Timo Werner - who moved in from RB Leipzig - handling a tough start to life at Stamford Bridge.
has scored five goals and provided five assists, and 23 chances created besides five big more chances created in 25 matches so far in 2020-21.
' performance this term had legend Frank Lampard dismissed and replaced by Thomas Tuchel, and Rolfes feels it is wrong to focus on
, who is trying to show his strength in the Premier League.
"It's always difficult if you change country and a little bit of a different style. That's the same if we sign players,"
"Some players need two days, some guys need half a year. For example, Moussa Diaby needs three-four months to adapt from France, although he was playing for PSG, to adapt to the Bundesliga.
"You have to have in mind when you sign players, that not everybody is directly from the first day there.
"I've followed Chelsea a little bit from a distance, but it's not only Kai or Timo Werner struggling a little bit, it's also the team – they expected more from the whole squad.
"That's not so easy if it's not working in the team and you come in as a new player. It's much easier if the team is working and you step in your best position.
"That's a process for Kai, to adapt to England and the Premier League. There is no doubt Kai is a fantastic player and has all the ability to play on the world-class level and although it's probably not his best six months, there is no doubt in my opinion."