“I am happy for him because he worked very well in the last month”
Pellegrini said: “It was a very unlucky injury because it was in a training session without any problem.
“He shot a ball and he felt that something happened in his muscle, and it was a very hard injury.
“I am happy for him because he worked very well in the last month. He returned maybe a little bit earlier than the doctor expected, that’s why he is not in the Champions League list and I changed him for Kelechi (Iheanacho).
“I hope in the last games of the Premier League he will demonstrate how good a player he is.”
Nasri will start against the Baggies with David Silva and Raheem Sterling both injured and Kevin De Bruyne due to be rested following his own successful comeback from a six-week absence.