Ex-Manchester United defender Jonathan Spector says Cristiano Ronaldo was a "frustrating player" during his initial days at Old Trafford.

Ronaldo has gone on to become one of football's greatest ever players, and Spector says none of that would have been possible without the environment created by Sir Alex Ferguson.

"He was a frustrating player. You could see that he had so much ability but that he wasn't a finished product just yet," Spector said exclusively to AmericanGambler.com.

"I think he owes a lot for the player he is today not just to the manager but the players that were around him. [Sir Alex] Ferguson did a great job of having players in the team that could help the players around them, make everyone around them better players. I think those formative years in his development to make him the finished product; he couldn't have been at a better place than Manchester United.

"You could see his final ball wouldn't quite be there, you could see at times Ruud Van Nistelrooy might get really frustrated because he didn't know how many step-overs Ronaldo was going to do before putting the ball into the box for him but his ability on the ball, to beat players one-on-one, it was clear to see that he was going to be a very special player."