Rihanna thinks Karrueche Tran is no threat to her relationship with Chris Brown.

Although Chris has been spending time with his model ex-girlfriend recently, the 'Diamonds' singer isn't worried as she reportedly thinks Karrueche isn't in her league.

A friend of Rihanna's told HollywoodLife.com: ''''Rihanna is not stupid and she know his little side piece is there but she ain't tripping on the small stuff and trust, it's really small. Ri don't even pay attention to that because there's no point.

''She would never give time or spend a second thinking about another girl that's not even in her same league. Come on now, there's really just no comparison and she could care less because she and Chris know what time it is!''

Chris - who he is still on supervised probation for assaulting Rihanna in 2009 - has been inseparable from the 24-year-old singer recently, with Rihanna even flying out to Europe to spend time with him on his 'Carpe Diem' tour and the pair regularly post intimate snapshots of each other on Twitter.

The singer dumped Karrueche in September to concentrate on his friendship with Rihanna and reportedly gave her a generous payout following their split.