Michael Owens claims there is still a question mark over Anthony Martial's ability to play as a No 9 despite the Frenchman bagging a hat-trick against Sheffield United.
Martial's treble means he has now scored 19 goals this term - the same number as Marcus Rashford.
The Englishman will have been upset not to get on the scoresheet having spurned an excellent early chance.
United have found form in 2020 after struggling for much of last year.
Ole Gunnar Solskjaer has sought to address several problems that exist in the Red Devils squad, but Owen, who scored 17 times for the Old Trafford outfit, reckons their forward line still needs reinforcements.
He told Premier League Productions : “[Marcus] Rashford missed a chance in the first half and if he had put it in, it would have been one of the goals of the season. The intricate play on the edge of the box was absolutely brilliant.
“So now I think he’s [Martial] going to get more service, and now is the right time to be playing as a centre-forward for Manchester United – with the likes of [Paul] Pogba and [Bruno] Fernandes and all these players in and around you.
“Is he one that’s going to be the No.9 for years to come? At the minute he looks very inconsistent. He will score a hat-trick, but is he going to constantly score a lot of goals? There is still a question mark.
“There is still a question about what is his best position. I think it’s probably off the left, but then again that’s probably Marcus Rashford’s best position.
“They are shuffling the pack a little bit at the moment but if you ask most people, they will say: ‘Where do Manchester United need to strengthen? They need a main No.9’.”
Having lost Romelu Lukaku and Alex Sanchez in the summer Solskjaer has previously admitted they would add in attack.
Odion Ighalo arrived on loan in January but will only remain in Manchester until the turn of the year.
