West Ham boss Manuel Pellegrini admits he was left frustrated by a halftime injury to Samir Nasri in defeat at Chelsea.

Pellegrini was ready to turn to the French winger to boost his side's chances of getting back into this tie.

But the former Manchester City and Arsenal man picked up a calf injury during the interval.

Pellegrini said: "Samir Nasri was going to start in the second half, but in the warm-up he felt a muscle injury in his calf and wasn't confident to play.

"We'll see tomorrow."