"It's inevitable he is leaving. There is so much interest in him - not just in this country but around the world," Bruce said.
"We are talking about the biggest clubs in this country and Spain and beyond.
"There was a loan deal put to us by Real Madrid but it was not acceptable. We do have someone in mind to come in, but that is five months off."
United were said to have made their interest in the attacking midfielder, who can play on either wing, during the January transfer window.
However, a report in the Mirror
claims Bruce met with his former United manager Sir Alex Ferguson to persuade him to hold off making a bid until the next window.
Bruce would have been loathe to lose Valencia in the same window that saw Emile Heskey complete a £3.5 million move to Aston Villa and Wilson Palacios join Spurs for an undisclosed fee thought to be in the region of £14m.
Wigan, however, will be unable to retain Valencia's services beyond the end of the season if their £18m valuation is met by United.
Real Madrid could turn their attentions away from Valencia following last month's rejection and ramp up their efforts to sign Carlos Tevez instead.
The Mirror adds that Real want to lure the Argentina international away from Old Trafford and will match the £75,000-a-week offer United are prepared to pay Tevez to keep him.