The fit-again midfielder has made substitute appearances against West Ham and Manchester United after missing five weeks with ankle and hip injuries.
It was put to Mousa that it must have been frustrating to miss out on high-profile matches against the likes of Real Madrid and Liverpool in recent weeks.
“It’s been tough, of course,” he said. “It’s frustrating not only missing the big games but you just want to play.
“I can’t get too carried away because of the result but I played half-an-hour against Manchester United and that’s positive for my physical condition.
“I thought I started well this season so the injuries have been frustrating but the team has been doing well.