Nemanja Matic insists he had nothing to prove to Chelsea and only wanted to show he "deserves" to wear the Manchester United shirt at Old Trafford.
Matic left Chelsea for United in a £35 million deal in the summer after winning two Premier League titles at Stamford Bridge, with United winning the meeting between the two sides 2-1 on Sunday.
"I played for Chelsea for three-and-a-half years and I gave my best to win against them and show my quality again," Matic said. "I didn't have anything to prove to them. I wanted to show my new club that I deserve to wear this Manchester United shirt.
"This was a big win and I hope the team will continue like this because every game in this league is a war."
There was speculation in the summer that Matic wanted to leave Chelsea because he did not feel appreciated despite playing his part in lifting four major trophies. However, he is still staying tight-lipped about the reasons behind his move.
He added: "I don't want to speak about why I left Chelsea. I will keep that to myself. I'm happy in Manchester and that's it. Moving to United was good for me. I play for a big club."