Ronaldo has reportedly told the United hierarchy he wishes to move on should they receive a suitable offer this summer.
The 37-year-old has not reported for pre-season training as scheduled this week and is not part of their travelling party to Thailand this weekend.
Ronaldo is the top scorer in Champions League history but he faces missing out on the tournament next season if he stays at Old Trafford following Manchester United's sixth place finish last term.
Ronaldo scored 24 goals in all competitions for United last season after returning to the club from Juventus for a second spell.
Ferdinand told his FIVE YouTube channel: “Of course he's not happy! You're talking about Cristiano Ronaldo here! I don't understand how it's a big story that Ronaldo is not happy with the way things are at Man Utd. He can't be. I wouldn't be.
“Anyone who wants to win football matches or trophies, anyone who is used to winning and competing every year at the top of the table for the biggest prizes, and then all of a sudden isn't - and doesn't even qualify for the Champions League - you can't sit here and expect them to be happy.
“He's not happy with missing out on the Champions League, he doesn't even know what the Europa League soundtrack sounds like! When that comes on, he's going to be thinking ‘what dance am I in here?’”
Ferdinand added, with Ronaldo yet to return for pre-season training: “I've been seeing people being a touch disrespectful. The way that people are questioning 'he's not here' and the hysteria surrounding it. A member of his family is not well, so he's not at training.
“This is the most consummate, most professional athlete that we've seen on these shores. The most professional athlete we've seen for over 15 years and people are questioning this guy's professionalism and why he's not at the training ground.
“Yeah he might want to leave, he might not be happy with certain things at the football club, but in terms of professionalism, this guy is training where he is - we've seen the pictures.
"His family are there, he needs to be where they are and you have to respect that. Simple as. Could it have been communicated better by the club? Probably.”
