Martial has become disillusioned at United, losing the automatic starting berth he enjoyed in his first season under Louis van Gaal, having signed from AS Monaco in an initial £36 million deal in 2015.
Having found regular starts hard to come under José Mourinho, Martial looks set to depart the club this summer after his agent revealed last month that the 22-year-old wanted to leave in search of regular football.
The forward failed to make France's World Cup-winning squad and blamed his omission on his lack of game-time last season, which is why he wants to kick-start his career at a new club.
Whilst Martial is unhappy at Old Trafford, United's all-time leading scorer Rooney believes the Red Devils cannot afford to lose his quality.
Rooney, who is now on the books of MLS side D.C. United, told talkSPORT:
I think Martial, ability-wise, is incredible. But I think it's how do you get the best out of him?
Knowing Anthony the way I know him I think if you can get the best out of him, he's up there ability-wise with the best in the league.
I think sometimes it is difficult to get to know him as a person, as a character because of the way he is.
But I think once you do get to know him, you just keep him happy.
When asked if Martial was in a similar predicament to France and Arsenal legend Thierry Henry, Rooney had one simple answer.
Yeah, I think Anthony could be at that level.