That's the view of Liverpool legend John Barnes, but it's one that many Man United fans might well back as the undeniably gifted French striker continues to blow hot and cold at the club.
Martial has struggled this season, netting just four goals in 21 Premier League appearances, while the emergence of 19-year-old Greenwood - and the signing of veteran hitman Edinson Cavani - have meant he isn't necessarily first choice for an attacking spot.
The 25-year-old started on the bench in Sunday's 0-0 draw with Chelsea, with Greenwood given the starting spot by Ole Gunnar Solskjaer. Martial was brought on for just the last 11 minutes. Post-match, Sky pundits Graeme Souness, Roy Keane and Jimmy-Floyd Hasselbaink questioned the player's hunger and passion for the game.
Now Barnes has added his opinion, claiming a fresh start could be best for both Martial and his current club.
"Anthony Martial has never been a centre-forward, despite Manchester United playing him there," said Barnes via BonusCodeBets.
"If he can't get a place in the starting team in his preferred wide position, following the emergence of Mason Greenwood, then maybe it is time for him to leave Manchester United.
"Lots of clubs nowadays have benches full of superstar players, who are happy to be there, but I don't know if Martial is one of those players, or what Manchester United's intentions are with him.
"But I would suggest a change could be good for both him and the club if they aren't getting what they want from him playing there."
Martial arrived at Manchester United from Monaco in 2015 for a record fee for a teenager (£36 million, rising to a possible £58 million). He made an instant impact by scoring a superb goal in a 3-1 win over Liverpool on his debut, but there have been plenty of ups and downs since.
The United No 9 netted his best return last season when he scored 23 goals in all competitions and finally looked to be utilising the pace, skill and finishing ability he's always possessed.
But this season has seen Martial once again struggle for consistency and come under criticism from pundits and his own side's fans.
Few people doubt Martial's potential as an outstanding striker. But - if Barnes is right - a change of scene this summer may help the player's form and give room for the likes of Greenwood and United's other strikers to make the centre-forward spot their own.
All imagery: PA Images
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