Marcelo accidentally breaks an opponent's leg in horrible incident, leaves the field in tears

Marcelo broke down in tears as he accidentally broke an opponent's leg, with fans calling the injury 'one of the worst' they have ever seen.

Fluminense played out a 1-1 draw with Argentinos Juniors in the first leg of their round of 16 Copa Libertadores clash on Wednesday.

Gabriel Avalos gave Argentinos Juniors the lead in the 14th minute, with Samuel Xavier Brito levelling three minutes from time.

Both teams were reduced to 10 men as Alexis Martin Arias was shown a red card in the 76th minute while former Real Madrid star Marcelo received his marching orders just before the hour mark.

The Brazilian was attempting a dribble then planted his left foot on Luciano Sanchez's leg in a sickening moment, which broke the player's leg.

Check out the video below (WARNING: Video contains graphic images):

The match referee brandished a red card to the 35-year-old, who cut a hugely emotional figure following the incident.

He left the pitch in tears and looked devastated as he inadvertently inflicted a horrible injury on the Argentinean.

After the game, Marcelo took to social media to wish Sanchez all the best in his recovery.

"Today I have had to live through a very difficult moment on the pitch," he tweeted. "I have inadvertently injured a colleague. I want to wish you the best possible recovery, Luciano Sánchez. All the strength in the world!"

Needless to say, the incident between Marcelo and Sanchez sent social media wild.

One Twitter user wrote: "This is excruciatingly horrible, and prayers for Luciano but there is no way in hell that’s a red card. I mean it’s not even a foul. Yeah the result is awful, but all I see is a dribbler planting his foot mid stride in a spot a defender decides to slide his leg into."

A second tweeted: "I feel bad for Marcelo. He knows that could be a career ending injury."

A third added: "Marcelo isn't even trying to step on him either bro, this shit is just so unfortunate."

A fourth said: "This was hard to watch and one of the worst injuries I’ve seen."

Another commented: "Nastiest leg break I've ever seen."