DERBY, England (AFP) - Sir Alex Ferguson has issued a fresh call for greater protection for Cristiano Ronaldo after his star player defied another physical buffeting to push Manchester United back to the top of the Premier League.

Ronaldo's 31st goal of the season proved decisive in a 1-0 victory over Derby on Saturday and ensured the Portuguese winger had the final word over the latest opponents to try and blunt his attacking menace with brute force.

Just a week after the Portuguese midfielder voiced concerns about him being able to remain in English football, because of the number of times opponents use illegal means to stop him, he was singled out for some more rough treatment at Pride Park.

Derby's Darren Moore and David Jones were both booked for fouls on Ronaldo in the opening 22 minutes of the game, much to the annoyance of United manager Ferguson, who is growing increasingly angry at the methods being utilised to blunt his major weapon.

But Ferguson also believes that Ronaldo should have more faith in the game in England and believe that there is no way that the Premier League will allow someone with his phenomenal talent to be driven out of the country.

"It is important that he trusts the game itself more. People want to see footballers like him in our country and we have to give them encouragement to keep doing what they do best and tell them not to stop doing it," said the Scot.

"He has courage beyond belief. I never question that about him. I don't know how many times he has been fouled in recent games and I know that he was talking about his future after the Portsmouth games and said a few things.

"He has the courage to get up and get on with it and again we were left thanking him for the goal. He had so many chances to score, but he kept going and he eventually scored with the most difficult chance he had. That says a lot about his character."

Ronaldo had 11 chances in all against the Premier League's bottom club - but had to wait until his ninth opportunity 15 minutes from time to spare United from the embarrassment of dropping points to Paul Jewell's condemned side.

Arsenal's failure to beat Middlesbrough means that United can open up a three-point gap when they play Bolton at Old Trafford on Wednesday night, which could prove to be a significant move in the title race.

"Hopefully we can win that game and stay at the top of the league. The whole thing is bubbling up very nicely at the moment," added Ferguson.

At least, for the first time in many months, there was no shame in defeat for Jewell's side, who could easily have won the game themselves and forced young England goalkeeper Ben Foster into three fine saves on his United debut.

And Jewell wants his side to maintain the same levels of consistency for the remainder of the season, if they are to have any hope of beating the worst points total of 15 set by Sunderland.

"At last we have shown some pride and we have turned up for the fans, but there is no point us just doing it for one game. We have to do that for every game between now and the end of the season," said the former Wigan boss.

"I have been saying for some time that my players are not as bad as the results suggest and I felt we lost with some dignity. If we continue to play like that then we can get another six or seven points before the end of the season."