Imagine even thinking about doubting Cristiano Ronaldo.They won’t admit it now but there were some fans questioning why Manchester United were bothering re-signing the 36-year-old.The transfer fee of £12.9 million wasn’t exactly breaking the bank but is it sensible to pay him almost £500,000-per-week?ENTER GIVEAWAYWell, we probably got the answer during his second debut.Ronaldo scored twice as United beat Newcastle 4-1 at Old Trafford in a dream return of the Theatre of Dreams.This isn’t any 36-year-old.This is a man in such incredible shape that he could play at the very highest level for many years to come.There’s no better evidence of that than during his second goal.Can you answer these 12 questions about Cristiano Ronaldo's first spell at Manchester United?Ronaldo produced some brilliant movement and speed to create space for Luke Shaw to slide the ball into his path.The former Real Madrid and Juventus man took the ball in his stride and fired the ball through the legs of Newcastle goalkeeper, Freddie Woodman.While it wasn’t the finest goal of his career, the way he created the opportunity for himself deserves some attention.And it’s certainly been given the attention it deserves.Close-up footage of Ronaldo’s movement shows how he escaped - and then outpaced - the Newcastle defence.Video: Close-up footage of Ronaldo's movement for second goal

You can’t really appreciate just how fast Ronaldo runs during that close-up clip. However, BBC Sport were on hand to reveal that he reached a speed of 20.2mph (32.5kmph).

A gentle reminder that he’s 36-years-old....

Incredible.

After the 4-1 victory, Ole Gunnar Solskjaer heaped praise on Ronaldo and claimed he's "miles better" than when he left Old Trafford 12 years ago.

“He’s a different type of player to when he left but he’s still a ruthless and clinical goalscorer,” Solskjaer said. “He smells the big moments and when there are goals in there. He’s developed into a miles better footballer than he was when he was [first] here.

“Sometimes he can drift off to the sides and get turned and finish from there. You’re not going to use him as a battering ram, are you? He senses the big moments, when to run into the box and when to run in behind. He played very simply and didn’t give many balls away. I think he gave one away.”

RONALDO ON FIRE! Manchester United 4-1 Newcastle (The Football Terrace)