The young centre-back joined the Rams in January and has made seven appearances so far, but is being used sparingly by the former United skipper. He was an unused substitute in the recent 2-0 home victory over Luton Town, having started and impressed in the previous match at Stoke.
And in an interview with The Derby Telegraph, Rooney has dropped a big hint that United would be willing to extend the loan into next season.
‘He has been excellent in the games he has played,’ Rooney said.
‘He is young and I think this experience is great for him – playing, being on the bench, being around the first team, it’s a lot of pressure which he has handled really well.
‘Teden will play more games for us, he is a player I am hoping to keep here for next season.
‘He has gone from playing under-23 football to playing competitive football where there is a lot at stake. He is getting a good amount of minutes, but it is important I protect him as well.
When asked if he had spoken to United about keeping Mengi at Pride Park next season, Rooney replied: ‘Yes. It is on the player, really.
‘I want to make sure we finish the season strong and then it is a decision for Teden to make.
‘Of course he has to see what Manchester United’s feelings are on him, and what his feelings are.
‘I feel he has improved a lot and he has shown he can play at this level. Whether he is happy to go back and sit on the bench and play Carabao Cup games or whether he wants to further his experience and play in a very tough league, it is down to Teden.’
Another issue, of course, could be whether Rooney himself will still be at Pride Park next season. Derby are currently struggling in 18tgh place in the Championship and pressure is mounting on the United legend as the season draws to a close.