There have been few fairytale rises at the rate of the precocious striker’s, having gone from a first Manchester United appearance to scoring on his England debut in the space of 92 days.
An FA Cup winners’ medal and new contract at Old Trafford came either side of Friday’s strike against Australia, which went some way to securing his place in Roy Hodgson’s 23-man squad.
Rooney knows a thing or two about shining at a young age and believes his Red Devils team-mate deserves his place in the 23-man group, despite his tender years and inexperience.
“His attitude is fantastic. He’s really been left to play, and he’s done really well. I strongly believe he deserves his place in the squad,” Rooney said.
“He can be a dangerous player for us. He had a fantastic debut, scoring after two or three minutes. I think, as players, we appreciate how tough the decision was for Roy to make. But with Marcus, he’s a strong-minded lad for 18, and he can certainly bring a lot of fear to defences for us when he plays.
“If he keeps going the way he is, he’ll be a massive talent for England and Manchester United for a good few years.
“I think the way he took, first of all, to coming into Manchester United’s team and the way he has performed until the end of the season has been incredible, really, for his age.”
Rooney was in a similar position in Portugal at Euro 2004, when he sparkled as an unfettered 18-year-old as England made it to the quarter-finals.
His rapid ascent was, remarkably, relatively slow in comparison to Rashford’s, and the England captain hopes the country’s latest teenage star is allowed to blossom.
The pair lined up briefly together in the second half of the 2-1 win over Australia last week, and could again against Portugal at Wembley tonight, but Rooney has no intention of bombarding the younger man with veteran wisdom.
“With Marcus now in this tournament, for me he doesn’t need much advice. Let him play,” he said.
“As a young lad that’s how you’ll see the best out of him. In the future you can work on more advice, more instructions.
“With some players you just let them play and I think he fits that category.”
Rashford’s inclusion meant Andros Townsend and Danny Drinkwater joined the injured Fabian Delph in missing the cut on Tuesday – a “very difficult decision” for Hodgson as he plumped for an extra attacker.
The England manager insists Rashford’s goalscoring debut display was not the deciding factor in him making the squad, saying it came as a result of his impressive overall emergence.
“Rashford’s had that fantastic end to the season and he’s a very, very interesting player,” Hodgson said.
“He has special qualities. I think that’s been recognised by everybody and it’ll be very interesting to see, in a squad of 23, whether or not he can bring those qualities to bear at an even higher level.”
Rooney has seen his own position in attack come under question since the rise of Rashford, not to mention Harry Kane and Jamie Vardy.
But he retains Hodgson’s full faith, as captain and player, and declared himself happy with his preparations for France.
“It’s certainly as good as I’ve felt going into a tournament, and that’s largely because I’m injury-free,” the 30-year-old said.
“I’ve had little concerns going into previous tournaments playing on my mind, but I have no concerns about that now. I’m just looking forward to it.”