Uncertain future? Cristiano Ronaldo is reportedly unhappy at Real Madrid

Manchester United have been handed a boost with Cristiano Ronaldo reportedly 'restless' at Real Madrid.

The Red Devils have been linked with a summer swoop for the Portuguese superstar, who spent six seasons at Old Trafford before his £80million move to the Bernabeu in 2009.

However, Ronaldo has become frustrated with the lack of silverware at the La Liga giants this season, according to Marca, and could push for a move.

Paris Saint-Germain are keen to bring the 30-year-old to the Parc des Princes, but United could also make a move after this latest development.

Ronaldo smashed 117 goals in 290 games for the Red Devils following his £12.25million switch from Sporting Lisbon in 2003.

He has netted 58 times in just 53 games for Real this term, but his haul hasn't been enough to land any domestic honours or the Champions League.