Eye-sore: Bellator kickboxer Alex Avogadro suffers UNBELIEVABLE eye injury after being hit with flying knee (GRAPHIC)

Alex Avogadro won't forget his Bellator kickboxing debut in a hurry after he left the ring with a grotesque swelling of his left eye after opponent Luca Cecchetti drilled him with a flying knee during their fight on Saturday.

Cecchetti landed the technique in the first round of the fight in Milan. And, despite his eye bleeding profusely and swelling up almost immediately, the Italian bravely battled on after somehow convincing ringside medics that he was fit to continue.

However, it wouldn't last. The injury continued to worsen as the first round extended and it eventually became too much for even Avogadro as he was forced to concede the bout via injury TKO.

And as the below footage suggests, it seems he made the correct decision.

The technique, known as a 'switch knee', involves faking that you are going to attack with one knee before using it as momentum to thrust your other knee towards your opponent at full force.

It is regularly seen in mixed martial arts, perhaps most notably in July when Jorge Masvidal used the same skill to defeat Ben Askren just five seconds into their fight at UFC 239.