Sir Alex Ferguson has branded Ryan Giggs "truly unique" after the Manchester United legend decided to leave the club.

Giggs, 42, played in 963 games for the Red Devils before shifting into their backroom staff, which eventually saw him become Louis van Gaal's assistant manager over the past two seasons.

Van Gaal has since departed Old Trafford with Jose Mourinho appointed to be his successor, despite calls for Giggs to be promoted to the full managerial role.

However, the former midfielder has decided to follow a similar path to Van Gaal in leaving the club and Ferguson has since voiced his appreciation of Giggs' talents both on and off the pitch.

"At our club you don't play friendly games or easy games," the former Manchester United manager told the club's official website. "Each one is a cup final for the team we're playing against.

"So when you consider that Ryan had to run up and down that left touchline for over 20 years in matches of that intensity, he is truly unique. What he managed to do was completely unheard of.

"He became a hugely important figure within the dressing room. All the younger players would go to him because he commanded such respect and had such great influence on his teammates.

"His place in the history of Manchester United and football is already assured. I doubt we'll ever see a career like his again."

Ryan Giggs was also Manchester United's player-manager for four games towards the back end of the 2013-14 season. Getty Images

Ferguson wasn't the only Manchester United great to brand Giggs "unique," with former forward Sir Bobby Charlton also hailing Giggs' career.

"Ryan Giggs was a unique footballer," he told the club website. "He has been a credit to Manchester United and I don't think we will ever find his like again.

"It's incredible to think that he played past his 40th birthday -- back when I was playing, everyone just assumed that you were finished when you reached 30!

"For Ryan to play for so long and win so many honours was absolutely sensational. It has been an honour to follow his career."