"We have a lot of games every week and I think it is a clever decision [to rotate the squad]."
That rotation saw Di Matteo make six alterations for Tuesday's Champions League match at the Estadio da Luz.
The changes paid dividends as Chelsea will head into next week's second leg against Benfica in a comfortable position, which pleased Mata.
"It was a good result for us," the Spain international said. "It was a very, very important game, away, and a very important goal from Salomon Kalou.
"It is very important for us. The most important thing when you play away is to try and keep your clean sheet and then try and score.
"We did that but we have not finished the elimination and we have to fight at Stamford Bridge.
"It was fast, I tried to score and hit the post.
"I think we had a lot of chances to score and for us the 0-1 is a very, very good result.
"In the second half we had chances to score like mine. I hit the post, it was unlucky, but we got the goal.
"It is not over yet. Benfica for sure will come to our stadium to try to score. It's not over, we have to fight again."