The 30-year-old striker is currently sidelined with a knee injury after a brilliant start to 2016 for the United skipper after a return of five goals and three assists.
Rooney endured a mixed start to the 2015/16 season after he scored just three times in his first 14 games of the campaign.
According to a report in the Manchester Evening News, United are weighing up a proposal to sell their skipper to one of the clubs in the Chinese Super League.
Speaking to Newstalk’s Off The Ball, Giles explained why he believes the 20-time English champions should keep Rooney beyond the summer.
“Wayne Rooney has been their best player this season,” Giles told Newstalk.
“You’re still selling your best player. I know he is 30 now.
“What they want to be doing is sell and get a good price for the player that have failed.
“To be fair to Rooney, he has been their best player this season.”
Rooney has scored seven goals and has made four assists in 22 Premier League games so far this season.
The Red Devils captain is bidding to become United’s record goal-scorer and is five goals short of Sir Bobby Charlton’s record.
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