The 28-year-old suffered a dip in form last season despite collecting the club's player of the year award in the previous campaign of 2011/12, but manager David Moyes has been full of praise for his recent displays.
Valencia has been a prominent part of the United side since Moyes' arrival, featuring 23 times in all competitions, and he feels that he has been able to return to form having put his injury worries behind him.
"I suppose I set the bar high in 2012 and then I had a niggling problem with my back which didn't allow me to train properly," he told the Daily Mirror.
"There is no sign of that now. I feel great and have been able to train to my maximum and put in 100 per cent.
"That has been paying dividends in my game and I feel my fortune has changed since going back to the 25 shirt."