Manchester United manager Louis van Gaal confirmed on Sunday he would be interested in bringing Cristiano Ronaldo back to Old Trafford, six years after the superstar left for Real Madrid.

Van Gaal, quoted by several British Sunday newspapers, said: "We are looking at all players, not just Ronaldo. But these players are mostly ungettable.

"With Ronaldo, let's wait and hope. There is no trainer in the world that doesn't like him. He plays on the wings and he is fast, and scores goals."

Ronaldo cost Real Madrid a then world record fee of 80 million pounds ($122 million) when he left England in 2009 but he turns 31 in February and was off the boil in Saturday's 4-0 defeat to Barcelona where he cut a frustrated figure.

The Portuguese international is a three-time World Player of the Year and is Real Madrid's all-time leading goalscorer. In Spain, he has won one league title as well as the 2014 Champions League.

During his time under Alex Ferguson at Old Trafford, he helped United win three Premier League titles as well as the 2008 Champions League.

Meanwhile, van Gaal conceded United is far from pretty to watch after it ground out a 2-1 victory at Watford on Saturday thanks to Troy Deeney's late own goal.

Van Gaal's side has been criticised for its conservative style of play under the Dutchman this season, but its latest defensive display paid dividends at Vicarage Road.

It had taken an 11th minute lead through Memphis Depay and, although Deeney's 87th minute penalty ended a run without conceding of 10 hours, United snatched the points at the death when Deeney turned Bastian Schweinsteiger's effort into his own net in stoppage-time.

"I have changed the system," van Gaal said. "Our positional game was not so good and that was disappointing. I know some people think our positional game is boring but I think it is a way to disorganize the opponent's organization.

"I was very satisfied about our defensive organization. We didn't give more than three chances away, one in the first half and two in the second.

"Memphis and Jesse Lingard played a very good game. We could have finished the game much earlier. I have to say after the penalty, I thought we gave it away but then you see the spirit of the game.

"We created three chances in a row. It was an injection, the equalizer. I am very proud I am the manager of that team."