The debate over the justification for Cristiano Ronaldo's Champions League red card in Juventus' 2-0 win against Valencia will probably outlast whatever suspension he receives from UEFA, but what cannot be argued against is that the 33-year-old only has himself to blame for the mess he now finds himself in.

On first inspection, and then with the benefit of replays from all angles, Ronaldo's dismissal following his clash with Valencia's Jeison Murillo appeared soft.

But it was Ronaldo's stupidity and petulance in attempting to grab Murillo by the hair which gave German referee Felix Brych the grounds to brandish the first Champions League red card of the player's career.

It was a show of frustration by Ronaldo and he was punished for it.

He will serve an automatic one-match suspension when Juve host Young Boys in Turin next month, but the tears which followed his dismissal might be down to the prospect of him also missing an emotional return to Manchester United on Oct. 23 -- potentially his last chance to play at the stadium where he first made his name.

A UEFA disciplinary panel will decide whether to extend Ronaldo's suspension, and it will be a huge blow for the player and Juventus, as well as the spectacle of the Champions League, if he is absent at Old Trafford.

But has this been coming? Was Ronaldo's petulance rooted in a realisation that his powers are declining and that he can no longer do what always came so naturally?

Add to that the pressure of being the man signed to end Juventus's long wait for another Champions League title, and a slow start to his career at the club after leaving Real Madrid this summer, it is perhaps no surprise that even Ronaldo is showing signs of feeling the heat.

But one thing for certain is that the incident in Valencia was not an isolated one.

Rewind to late June and Portugal's World Cup group encounter with Iran in Saransk -- a game that ended with Ronaldo embroiled in controversy following the failure of Paraguayan referee Enrique Caceres to send him off for an elbowing incident with Iran defender Morteza Pouraliganji.

Ronaldo escaped with a yellow card on that occasion, prompting Iran coach Carlos Queiroz -- a man who played a crucial role in Ronaldo's development at United during his time as assistant manager -- to angrily insist: "Elbow is a red card in the rules, the rules don't say if it's Messi or Ronaldo."

Ronaldo had a penalty saved earlier in that game and Iran proved a tough nut to crack, so his frustrations were perhaps understandable, but in his younger years, he would have reacted by scoring a crucial goal or making a decisive pass rather than lashing out at an opponent.

Juventus' star man looks bemused as he is dismissed. David Aliaga/NurPhoto via Getty Images

And the same applies to his clash with Murillo in the Mestalla on Wednesday. Murillo and Ronaldo had engaged in a grappling match inside the penalty area, Ronaldo couldn't shake him off and the Valencia defender then fell to the ground.

Ronaldo didn't need to take it any further, but by grabbing at Murillo's hair, he showed how the Colombian had got under his skin.

During his six years at United, the one quality that Sir Alex Ferguson always cited above all others when discussing Ronaldo was his toughness.

Forget the skills and goal-scoring brilliance, Ferguson loved Ronaldo's ability to respond to all kinds of physical intimidation in the best way possible, by coming back and punishing the opposition with his talent.

He still possesses that toughness and the ability to change a game in an instant, but he is less mobile than he once was and lesser players have now discovered that there are ways to stop, or hold up, Ronaldo.

The incidents against Iran and Valencia are testament to that and Ronaldo is struggling to find a way to respond as he was once able to.

But at least he cares. When compared to Neymar's anaemic performance for Paris Saint-Germain at Liverpool 24 hours earlier, Ronaldo was clearly busting a gut to make a difference against Valencia until he was sent off.

He is desperate to succeed in Turin and he will probably be as annoyed by the prospect of missing out on scoring two penalties -- both were converted by Miralem Pjanic against Valencia after Ronaldo was sent off -- as much as forcing his teammates to play with 10 men for over an hour in Spain.

But time is catching up with Ronaldo and both he and Juventus know that the big outlay for him is a short-term gamble aimed at hitting the jackpot of Champions League glory.

It is a heavy burden for a player to carry, even one as great as Ronaldo, and the strain showed against Valencia.

Yet maybe it is a timely lesson for him. He is still a game-changer and a ruthless finisher, but he can't do what he did at 25 and if he accepts that and remodels his game accordingly, he can cut out the petulance which threatens to cost him dearly.