Gary Neville believes Ole Gunnar Solskjaer should insist upon strengthening his squad in January.
United were held to a 3-3 draw by Sheffield United on Sunday, leaving them nine points adrift of the top four after 13 matches.
The Red Devils have won only one away game in the Premier League this term, despite having not yet faced any other member of the big six on the road.
Solskjaer recently downplayed rumours that United could be set for a mid-splurge when the transfer window reopens at the start of 2020.
But Neville thinks the current squad lacks experience and has called upon his former team-mate to splash the cash as United target Champions League qualification.
"They haven't got senior players to let them [the younger players] know the expectation of what's required in a football team," he told Sky Sports.
"They haven't got the leaders and those around them that set the standard. When I first broke into the team, I had people who set the standard, let you know where to go.
"[Juan] Mata is on the bench, [Paul] Pogba's injured, [Nemanja] Matic is looking to get away, [Ashley] Young's on the bench - the experienced players at the club are in turmoil a little bit. They haven't got futures, some of them. Others are injured. So essentially they're all out on that pitch, young together.
"There's another thing - they don't know how to approach a Premier League away game. They don't understand that it's different playing at Old Trafford than away from home. They don't have the experience or maturity. Ole Gunnar Solskjaer has to go and spend the club's money for himself, on two or three experienced players.
"He must demand it, he's not going to be there to see the fruits of the labour that he's putting in because there's a lot of good young players on that pitch that I enjoy watching, but unless they get the players in and around them quickly, they'll not see the standard and won't have the maturity.
"Ole's going to have to be selfish. He's going to have to have that ruthless streak that a [Jose] Mourinho has, or a [Antonio] Conte has, and he's going to have to go and spend the club's money in the January window and put two or three experienced players in that group and they could come alive."
United face Astana in the Europa League on Thursday, before welcoming Aston Villa to Old Trafford next weekend.
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