Real Madrid star Cristiano Ronaldo thinks La Liga is the toughest league in the world - and rates last season's title triumph as the greatest of his career.

The Portuguese star, who is on holiday in Thailand, admitted he believes La Liga is a more difficult test than the Premier League. The Madrid ace scored 46 goals last year and played an integral role as Jose Mourinho's side won their first league title since 2008.

Ronaldo spent six years with Manchester United, winning the Champions League in 2008. His move to Real Madrid made him the world's most expensive player, after Madrid shelled out £80m to bring him to Spain.

Ronaldo and co broke Barcelona's stranglehold on Spanish domestic football this season, and the Portuguese star rates that achievement as the best of his career so far.

"I think the best moment so far was winning La Liga," said Ronaldo. "Because I think the Spanish league is the hardest in the world. It has great teams like Barcelona and to finish nine points ahead of them…that says a lot."

Despite the relative difficulty of the league, Ronaldo has posted some remarkably impressive statistics. Since joining Madrid in 2009, the Portugal striker has scored 112 goals in just 101 league appearances.

The Portugal captain could be joined by Manchester City defender Micah Richards at the Bernabeu next season. The Team GB right-back has been linked with a move to Madrid, and Jose Mourinho is thought to be a big fan of the defender.

According to the Daily Star, a fee in the region of £20m has been mooted, but Manchester City are unlikely to be willing to part with the talented young fullback, who formed a key part of a miserly City defence last season.

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