Matic, who returned in January, was sent to the Portuguese giants in the deal that brought David Luiz to Stamford Bridge in 2011.
"Maybe if I stayed at Chelsea, I don't play like I do now - maybe I play better, maybe I play worse, you never know. But, for me, in that moment it was good to go and play.
"I learned a lot at Benfica, which is one of the biggest clubs in the world; not only how to play that central-midfield position, but I learned to play with pressure.
"There is a lot of that at the club, just like there is at Chelsea, and it was good for me to go.
"Now it is very nice to be back. It's a pleasure to be part of this team and to work with these players and coaches. All the people have been helping me since I came back and I'm very happy."
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