In his three starts since his return, Mata has scored twice and racked up four assists, playing a key part in two-thirds of Chelsea's goals.
Mata acknowledged he would eventually feel the benefit.
"Not now. Later. Maybe in January, February," he said.
"The season is so long for each player. Maybe these two weeks will be very important for me.
"We had a talk before the start of the season because, with the Euro cup and the Olympic Games, it must be a hard summer for me.
"So I think it was logical.
"Before I had these two weeks, I didn't feel bad. But I think, with so many games in the season, it will be good for me and now I feel very, very good.
"I think it was a nice break for me. Two weeks resting, trying to get out of football and now I feel really fit.
"I feel really well as well because of the good run of results for the team. We stayed at the top of the league, so I'm very happy."