Man United v Liverpool: Ronaldo happy to prove doubters wrong
Derby day closing in
Ronaldo moved back to the club at the end of the August transfer window after leaving Juventus and made a great start with two goals on his debut against Newcastle.
The former Real Madrid forward has also scored vital Champions League winners in home ties against Villarreal and Atalanta.
Ronaldo eager to help
However, United were poor in their last league game against Leicester, when they suffered a 4-2 defeat against Brendan Rodgers's side that heaped pressure on manager Ole Gunnar Solskjaer.
But Ronaldo has insisted he is not back in Manchester for a holiday and the 36-year-old Portuguese star believes he can play a key role in taking United back to the top.
He said: "I think the main thing is that I'm still happy and enjoying football.
"It doesn't matter how many things I have won in my career. I have won everything but I'm still motivated.
"I'm in a new chapter of my life, even with my age, and this is why I am here - to try to win.
"I think the club needs to be at this level of winning and aiming to win big things, so I'm here to help."