Rooney has also been among the substitutes in United's last three games under Jose Mourinho.
However, Giggs backed England's all-time leading goal scorer and outfield appearance maker to return to form, saying he was too good a player not to.
Sunderland striker Jermain Defoe has offered Wayne Rooney some advice on how he can extend his career at Manchester United. It was well documented the things he was doing, like yoga and Pilates.
"Ryan Giggs showed that, Teddy Sheringham played until he was 40, Les Ferdinand was 38".
"I just think, if you do it right, if you look after yourself like I always have then you shouldn't have a problem". People forget what he's done and how much football he's played.
You lose that pace as you get older.
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"At one stage, he was the wonder boy and now people are getting so frustrated the phones are burning".
Despite the recent criticism, Defoe maintains that his former England teammate is still one of the best players the country has ever produced.
Publicly, the Rooney camp insist he has no intention of leaving United before that massive deal expires and say he remains committed to the Reds and will fight to get back in their team.
In the first few games of the season, it seemed the 30-year-old had turned a new leaf, registering a goal or an assist in the first three league matches.
"So I think at Man United he feels at home. I know they are two totally different specimens and they have lived their lives in two totally different ways but if you look at him at 35, why can't Wayne Rooney still be playing for Manchester United at 35?"
Privately, however, there must be an acceptance that this marks the end of the road for him in Manchester, with the matter likely to be forced next summer if they do decide to let him go.