The Portuguese again hit out at Premier League chiefs following his side's goalless draw with Southampton on Wednesday night, claiming that he has not been helped by the way fixtures have been scheduled.
Souness has grown tired of Mourinho's complaints, however, telling him to simply "get on with it" rather than looking to manufacture excuses following what has been a disappointing first league campaign in charge at Old Trafford.
"We've all done it, we've all been there. It's the price on the ticket if you're winning trophies. If you get to the later stages of European cups... you have to deal with [lots of games]. It's nothing new in football," he told Sky Sports News.
"Big players have to say to themselves "I'm not tired." I mean it, I never ever felt tired. I think what happened if I did feel tired, it would be maybe we'd lost a couple of games and you started to feel sorry for yourself, and that would last a nano-minute.
"The more success we had, I couldn't wait for the next game to come along. The last thing I would want is a manager continuously telling me I'm tired. You're handing an excuse to your players to not play well. I talk from experience. People say the game has changed, but has it changed that much?'
"Was that a difficult game of football tonight?' he asked. 'No it wasn't. Was it a tough game against Tottenham at the weekend? It wasn't a terribly demanding physical game where they were getting knocks. Was it a physically demanding game against Arsenal the week before when you're sitting in there, not chasing the game? I don't see it. You deal with it and you get on with it. This is not a new problem.'"
United will play their 61st game of the season on Sunday when welcoming Crystal Palace to Old Trafford, before preparing for the Europa League final with Ajax three days later.