Yesterday Bournemouth welcomed Arsenal n the FA Cup fourth round.
This was the first-ever FA Cup meeting between Bournemouth and Arsenal, and only the 12th meeting overall between the sides.
The Gunners opened the score line in the 5th minute as Bukayo Saka placed the ball into the net after an assist from the other youngster Gabriel Martnielli.
The Gunners played well and they scored again.
Shortly after the start of the second half Mustafi was carried off.
Emiliano Martinez came to punch the ball, Mustafi landed badly, bending his left ankle and causing what will no doubt turn out to be ligament damage.
The 27-year-old Germany defender will have scans on Tuesday to determine the extent of the problem, but Arteta conceded the early signs were not positive.
The Gunners already have problems in defence with Colum Chambers, Sead Kolasinac and Kieran Tierney all out injured.