Arsenal manager Arsene Wenger believes that defender Per Mertesacker needs time to settle in at the Emirates.
The German international, who joined the North London side in August, allowed Norwich City to take the lead at Carrow Road on Saturday before Robin van Persie rescued the tie to win 2-1.
"[Mertesacker] had not completely recovered [from the internationals]," Wenger told the club's official website. "It is a different game in England, a very demanding game for the defender.
"In every second of the game you are really tested with full commitment, and it takes some time to adapt We have seen that with [Laurent] Koscielny, who played at right-back and was exceptional.
"Last year he would not have delivered this kind of performance because you learn that from fighting in every game. That is why it is so difficult to buy defenders from abroad."
The Gunners turn their attention to the Champions League this week as they take on Borussia Dortmund at the Emirates on Wednesday.
Danielle Joynson
