Alan Shearer believes Ole Gunnar Solskjaer is taking a major gamble by not replacing Romelu Lukaku.
Manchester United let Lukaku join Inter Milan in a £72m deal this summer with fellow attacker Alexis Sanchez following his teammate to the San Siro.
It means United are desperately short of cover for Marcus Rashford and Anthony Martial, with youngster Mason Greenwood appearing the only replacement.
Shearer believes it could prove costly for United, who have managed just one win from their first four matches of the season.
"It is a big issue for United because they have taken a huge gamble by not replacing Lukaku," Shearer told the Sun.
"Going into the season with just Marcus, Martial and Mason Greenwood is very risky and that is a huge burden for those three to carry over a long campaign."
Shearer's comments come after England boss Gareth Southgate insisted Rashford was best coming from the left, after impressing in the victory over Bulgaria.
He backs Southgate's assessment that Rashford 'is not a No.9' - which leaves United with no out-and-out striker.
"There is no denying he is an excellent talent but I don’t think he is a natural goalscorer. We sometimes forget he is only 21 so time is still on his side," Shearer added.
"Even this season, when Manchester United’s main striker Romelu Lukaku left, boss Ole Gunnar Solskjaer plays Anthony Martial down the middle."
Rashford is expected to keep his place in the England side for their next Euro 2020 qualifier against Kosovo on Tuesday.
