Ireland will open their Six Nations campaign in the Aviva Stadium against Wales on Sunday, and it's undoubtedly going to be a physical encounter. 

One man who knows that better than many others is former Ireland captain Brian O'Driscoll, who remembers one particular occasion when there was a huge collision between himself and Wales' Scott Williams.

It being Throwback Thursday, O'Driscoll shared an image of the aftermath of that hit back in 2014, which left the Ireland legend with quite a bruise all across his "hoop", as he puts it himself.

 

#tbt to Wales game 2014 when @scottwilliams_1 nearly killed me & this happened when I landed on my hoop! #gascrack

A photo posted by Brian O'Driscoll (@13rianodriscoll) on Feb 4, 2016 at 5:22am PST

For his part, Williams didn't come off all that much better, and he responded on Twitter with a picture of his x-ray, as he also had to come off the field with a shoulder injury and required surgery afterwards.

Never been in a car crash but that can't have been far off one!! Came off second best though...... https://t.co/TULQp0TPQn

— Scott Williams (@ScottWilliams_1) February 4, 2016

.....@BrianODriscoll #onewayout #flatout pic.twitter.com/tQ87JDU7ww

— Scott Williams (@ScottWilliams_1) February 4, 2016