Ronnie O'Sullivan Reaches World Snooker Championship Semi-Final After Mark Williams' Incredible Moment Of Sportsmanship

Williams owned up to touching the yellow in a crucial frame versus O'Sullivan on Tuesday.

The 45-year-old poked the yellow ever so slightly which went unnoticed by the referee.

However, the Welshman alerted Jan Verhaas who announced a foul during a key moment of the match.

"I touched the yellow," Williams told Verhaas who replied: "Did you? Thank you," before confirming a foul which resulted in a four-point penalty.

Needless to say, Williams' brilliant gesture got fans talking on social media.

One Twitter user wrote: "Always been a class act has Mark Williams even at a crucial stage he had no hesitation to show his integrity."

A second tweeted: "Fair play such a crucial stage, a show of pure class that."

A third added: "It didn't look like he touched the yellow to me. Fair play to Mark. That's good sportsmanship."

After sealing a remarkable 13-10 victory over Williams to set up a semi-final clash against Mark Selby, O'Sullivan said: "I love a semi!

"I'd lump on Selby because I don't expect to beat him, and that's not me trying to take the pressure off, I don't need to I've got nothing to prove.

"Just as a bit of insider information from me... I don't know how anyone can beat him."

O'Sullivan faces Selby tonight for a spot in the World Snooker Championship final.