Arsenal's record signing Alexandre Lacazette has struggled to adapt to the intensity of the Premier League, according to Arsene Wenger.
The 26-year-old moved to Emirates Stadium from Lyon in July for a fee that could reportedly rise to £52 million, making him the most expensive player in the Gunners' history.
The France centre-forward has netted eight goals in 19 league starts but is yet to fully convince for the north London side, although his manager is not concerned.
"It is always a surprise for the players," Wenger said of the adjustment required from new arrivals.
"You accelerate and play more and the body needs to get used to it, the mind as well. It's a difficult period, the first year, because the family comes over and it's a bit less football-orientated.
"But you get used to it and he has played many games until now and I would say that the physical pressure on the strikers here in England has become absolutely massive."
Chelsea also broke their transfer record to bring in Alvaro Morata from Real Madrid, and the Spain international has experienced similar difficulties after a flying start.
"It's normal," Wenger said. "Morata, like Lacazette, he fights. But in England you play against teams who are organised and can play physically with 90 minutes intensity. The defenders have become much quicker than before. They are all athletes now at the back.
"What he [Lacazette] has worked on is to cope with the intensity of the challenges. In France, if you go down it's a free-kick. In England, you go down and it's no free-kick. That is much more difficult for a striker to get used to.
"This guy is used to scoring 30 goals per year so at the moment, even if he says no, I am sure he is frustrated."