WATCH: Shock as Messi loses temper; head-butts opponent and grabs his throat

How Lionel Messi stayed on the pitch after this altercation during a friendly between Barcelona and Roma last night, we will never know.

No-one should get away attempting to head-butt an opponent and then putting a hand on their throat.

Amazingly, the Argentinian superstar was only shown a yellow card after clashing with former Newcastle defender Mapou Yanga-Mbiwa during the first half.

Messi is undoubtedly one of football’s all-time greats, but that’s no excuse for this display of temper.

Lionel Messi losing his head against Roma tonight. Imagine the uproar if Cristiano Ronaldo did that. http://t.co/HbClEcX6yu

— Football Tweet ⚽ (@Footballtweet) August 5, 2015

The general reaction was one of shock at such an uncharacteristic display from the normally easy-going player.

Is... is that you, Leo?

Messi head-butts and chokes opponent, only gets a yellow card. WATCH: http://t.co/0rWq4uZSUJ pic.twitter.com/7CnY3A9OlC

— FOX Soccer (@FOXSoccer) August 5, 2015

I feel like if Messi grabs your throat out of anger you should just never play soccer again.

— Collin Crown (@CollinCrown) August 6, 2015

Although there were suggestions he might be spending too much time with one notorious team-mate.

WTF Messi! Channeling his inner Zidane?! Or is Suarez having too much of an impact on him! https://t.co/6HfhZSIGlT

— Zenia D'cunha (@ZENIADCUNHA) August 6, 2015