Rooney wants greedy Rashford, has high hopes for Martial
Rooney ended a 13-year association with United before the start of this season, departing as the club's record goalscorer for a return to boyhood club Everton.
The ability and potential of Martial and Rashford, 22 and 20 respectively, was part of the reason for Rooney seeking a fresh start for the final chapter of his career as his first-team opportunities dwindled.
The former England captain believes United's future is in good hands but encouraged Rashford, who has been used predominantly as a wide attacker by Jose Mourinho despite making his first-team breakthrough as a striker, to leave the defensive work to those further back in the team and concentrate on lifting his goal tally.
"Sometimes, early on in my career I was working too hard tracking back and Alex Ferguson sat me down," Rooney explained in an interview with talkSPORT.
"It does affect when you're in the opponents' box. You're a bit leggy. Alex Ferguson told me not to do so much work and be ready for when we get chances.
"I feel with Rashford it's maybe a bit of the same. You see him going back into the full-back areas.
"It's great he's got that enthusiasm but, to get the best out of him going forward, he maybe needs to let the defenders and the midfielders do it."
Martial was the most expensive teenager in world football when he signed for United in 2015 and, although Rooney acknowledges the Frenchman might not be the easiest player to read temperamentally, he insists his talent is beyond question.
Thanks to the fans for your amazing support #3Points pic.twitter.com/ga9ON5E3MK
— Anthony Martial (@AnthonyMartial) November 29, 2017
"Anthony Martial, ability wise, is incredible but it's a matter of how you get the best out of him," he said.
"Knowing Anthony the way I know him, I think if can get the best out of him he's up there ability wise with the best there are in the league.
"Sometimes it is difficult to get to know him as a person, as a character but once you do get to know him you just keep him happy. Anthony can be at that top level."
United travel to West Brom on Sunday, where they will look to claw back a portion of Manchester City's 14-point advantage at the top of the table.
Rashford scored his ninth goal of the season during last weekend's 2-1 Manchester derby defeat, moving him one ahead of Martial for the campaign.
"I feel that United at the moment have played some great attacking football and they're getting a bit of unfair stick," Rooney added.
"They're seeing games out at the right times. They've got some young players who are still learning how to break teams down."