The Ecuador international explained the motive behind his switch during a recent interview with MUTV as he bids to recapture the form that saw him sweep the boards at the club's 2012 annual award ceremony.
With his performance against Bayer Leverkusen in David Moyes' first Champions League group game a particular highlight, there are signs that Valencia is ready to shine for the new manager.
"I just think Antonio has been very honest," Robson told ManUtd.com. "Maybe he did feel a little bit of pressure when wearing the number seven.
"He won Player of the Year when he wore no.25 and, after an indifferent season for him, when he didn't always show the quality we know he's got, maybe there's a little bit of superstition to go back to the shirt he was wearing.
"So it's a good decision and a strong decision by him. I think he's started the season pretty well so that is good for the club and good for Antonio."
In regard to the vacant no.7 shirt, Robson is keen to see who will wear the famous shirt next. "For me, if we can sign a player who is capable of wearing that no.7, like a David Beckham or Cristiano Ronaldo, then great," said the United ambassador. "Hopefully, it could be Ronaldo again!"