Former Manchester United midfielder Phil Neville feels it would be "criminal" if out-of-favour left-back Luke Shaw does not fulfill his potential at Old Trafford.
Shaw has found himself frozen out by manager Jose Mourinho this season, struggling to convince the United boss he is worthy of a regular starting role.
The 21-year-old England international has been limited to just 14 appearances in all competitions in 2016-17, though he is in the squad for Sunday's EFL Cup final against Southampton, having missed out on the Europa League trip to Saint-Etienne midweek.
Neville has called on Shaw to learn from Henrikh Mkhitaryan and Marcus Rashford, who have won over Mourinho at various stages of the campaign.
"It would be criminal if Luke doesn't make it as a Man United player, a crying shame," Neville told the Times. "The opportunity is there for him.
"United don't have a left back. Luke hasn't grabbed that opportunity and it's disappointing.
"You have to train, behave and be a professional to a certain level for Mourinho.
"Luke's obviously not doing it at a certain level consistently.
"Jose speaks well of Luke, says he's got the ability. But Luke's going through what Henrikh Mkhitaryan went through, somebody else Jose didn't really trust.
"Jose couldn't rely Mkhitaryan in big games, to track runs, to play as part of the team."