The 40-year old Welsh midfielder has ended a stunning career that began in 1990 and delivered 13 Premier League titles, four FA Cups, three League Cups and two Champions Leagues.
Although initially surprised at Giggs' decision to retire, Beckham has backed the appointment of his former teammate as incoming boss Louis van Gaal's assistant following his four games in the managerial hotseat at the end of last season.
"I'm surprised he's retired because he was still playing great. Physically he's still in great condition, to play for so many years at the top level you have to be in great condition," Beckham told Sky Sports News.
"Now he has a new role at the club and it was great to see him walk out as Manchester United manager for those four games.
"When you've got someone like Giggsy, who all the players respect and all the fans love, it makes a huge difference.
"His role now has totally changed and I'm sure he will find it an easy transition because he takes things in his stride, he's not affected by anything.
"He knows the club better than most people who are at Manchester United now."
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