Jose Mourinho gave an update on Heung-Min Son's injury after the north London derby on Sunday.
The South Korean star pulled up holding the back of his left leg after chasing a through ball with only 17 minutes on the clock at the Emirates. He got back to his feet, but unfortunately couldn't continue.
Asked about the issue in his post-match press conference after our 2-1 loss, Jose said: "I don't know how long it is. It's muscular. Muscular is always not easy. He's a guy who normally recovers very well from any kind of injury. It's an accumulation of matches. In the Europa League, I gave him 30 minutes rest, so 90 minus 30 is 60, but 60 is still 60. When you are in so many competitions, this is something that can happen."