The United manager suggested earlier this month that the club captain was injured and not fit enough to play.
But, while on international duty with Ecuador, the veteran defender claims his lack of minutes is down solely to his club boss.
"Right now I haven't been playing, but it's more of a tactical decision," he tol 'Area Deportiva'.
"The player who has been in my place (Young) has been playing well. You have to respect the decision.
"The only thing I can do is prepare and be ready for when he (Mourinho) needs me and be in the right condition to compete
"I'm calm right now and I know I'll get an opportunity to play again. The relationship with Mourinho has always been a good one."
Valencia scored the opening goal in Ecuador's 2-0 friendly win over Peru on Thursday night.