Chelsea midfielder Mata happy to taste action in Cup win
He admits he has found it frustrating being made to wait in the wings.
"I've been training hard but it is not the same," said Chelsea's reigning player of the year. "You improve your rhythm by playing games. It is different to play than it is to train.
"It is easy for me to focus on my football and just do what I have to do.
"For me, the only thing in my mind is to keep working, training hard, and improving as a player, and to keep scoring and making assists.
"That is what I did at Swindon.
"I was really happy for the team and the result. It was a good performance, we scored two goals and it was enough to get us through to the next round.
"It wasn't easy. Swindon are a team that like to play from the back - there were no long balls and they have quality."