Manchester United captain Wayne Rooney admitted on Friday that he knows little about new signing Anthony Martial, but backed the French teenager to prove a success at Old Trafford.

United sent shock waves across Europe on Tuesday when they bought 19-year-old Martial from Monaco for a reported initial fee of £36 million ($55.1 million, 49 million euros), which it is thought could rise to £58 million.

Martial's new France and United team-mate Morgan Schneiderlin revealed earlier this week that Rooney had asked him about the teenager and the England captain confessed to being in the dark about the striker.

"It's been well-documented I haven't seen that much of him play, so I can't really say too much on him," Rooney told reporters ahead of England's Euro 2016 qualifier in San Marino on Saturday.

"I obviously saw him last season against Arsenal (in the Champions League), where he had a fantastic game. Hopefully he'll be a great signing for us.

"He's got a lot of ability from what I've seen and I'm sure he'll be a good player for us."