McInally says Rashford has been carrying one of the biggest clubs in the world and believes the signing of the Tottenham Hotspur’s talisman would help transform the Red Devils.
The Manchester United academy graduate scored 19 goals in 31 appearances for United this season, before suffering a double stress fracture in his back against Wolves in January, but the Scot thinks Rashford is too young to shoulder such burden.
Kane has been linked with a move away from North London, with Manchester United being one of his potential destinations.
According to media reports, Tottenham chairman Daniel Levy is mulling a sale of Kane for a world-record fee of £200m due to the coronavirus crisis.
In an interview with Sky Sports, McInally labeled Rashford as a fantastic player and insist Kane’s arrival would alleviate his burden.
"Harry Kane would bring a presence into the team that they [Manchester United] haven't got," the 57-year-old said.
"Marcus Rashford is fantastic, he's carried one of the biggest football teams in the world, but he's too young to do it. He hasn't had any help.
"Bring Harry Kane into that team and there's a different dynamic at Manchester United. He would make them a shoo-in for the top four, and pushing the top two.