Former Manchester United defender Rio Ferdinand has labeled the club's decision to sell striker Javier Hernandez as a "big mistake" and "crazy" move that should never have happened.

Speaking on TNT Sports Mexico, Ferdinand, who played alongside the Mexican forward during their time at Old Trafford, praised Hernandez's work ethic and impact at the club.

"He was a great example to a young player to come to a different country, new environment, big club with big expectations and show that you have to work hard," Ferdinand said.

"This guy worked hard. He was concentrated, focused, he wanted to learn [and was] asking questions. [The] perfect example to any young player and it is no surprise to what he achieved [and] went on to do great things."

Ferdinand expressed regret over the striker's departure from the club, stating: "I wish he stayed at United longer. I think it was a big mistake for United to sell him, crazy to sell him. I don't know why they did but he was a magnificent player and defenders couldn't defend against him."

Hernandez, popularly known as 'Chicharito', joined Manchester United in July 2010 during Sir Alex Ferguson's tenure. The Mexican striker spent four successful years at the club before being loaned to Real Madrid by then-manager David Moyes for the 2014-15 season.

Following his loan spell at the Santiago Bernabeu, Hernandez was sold permanently to Bundesliga side Bayer Leverkusen by Louis van Gaal, who had taken over as Manchester United manager.

Ferdinand's comments come amid ongoing discussions about Manchester United's transfer decisions in recent years, with many fans and pundits questioning the club's recruitment and retention strategies since Sir Alex Ferguson's departure.