Shearer wrote in The Sun: "When Alex Ferguson bemoaned the loss of Tom Cleverley to injury early last season a few eyebrows were raised.
"He was basically saying it was a major blow to his side and their prospects for the season. This about a player who had performed in only a handful of games for Manchester United after a series of spells out on loan.
"Looking back, Fergie was spot on because his side never again played with the same explosive, attacking movement as they had done in those opening fixtures with Cleverley, 23, part of the team.
"He had helped to turn the tide in the Community Shield against Manchester City. Then he was central to four successive Premier League wins over West Brom 2-1, Tottenham 3-0, Arsenal 8-2 and Bolton 5-0.
"Ferguson was not just trying him out. He had in fact held him back using loans at the likes of Watford and Wigan to prepare him for the move up to the United first team."