Since the announcement, fans have being paying tribute to the great man on Twitter.

A leader, a warrior, a gentleman - @Paul_OConnell has played his last for Ireland. #ShoulderToShoulder #RWC2015 pic.twitter.com/xNmt6YqIpX

— Irish Rugby (@IrishRugby) October 13, 2015

Heart just fell again with confirmation that Paul O'Connell's RWC & Ireland career is over. One of a kind. Best of luck in his recovery

— Sinéad Kissane (@sineadkissane) October 13, 2015

Thank you for everything Paul O'Connell. My all time favourite Irish rugby player. #legend #leader #damniceguy

— Deirdre Farrelly (@Farrellydee) October 13, 2015

@Paul_OConnell Thanks for all the great memories. @AlanQuinlan1

— pat💙💛🇮🇪 (@oohaah) October 13, 2015

Gentleman trending in Ireland & I only thought of one man - @Paul_OConnell you did your country proud #IRE #RWC2015 https://t.co/112jUkUQpG

— Noelle ☘️ (@IrishGirl_06) October 13, 2015

Awful way to go but he couldn't have left a more indelible mark on World Rugby. #OConnell #Legend #ShoulderToShoulder #IRFU

— Dave O'Flanagan (@DaveOFlanagan) October 13, 2015

One man summed up the cruelty of sport.

Sport really is a horrible thing sometimes, @Paul_OConnell one of the greatest ever to play the sport, terrific servant to Ireland..

— Ben L (@purplebenny) October 13, 2015

While we all hope the team can put in a few more big performances, not least for the big man.

Gutted Paul O'Connell will miss the rest of the World Cup. An icon & inspiration. Let's win it for him! #ShoulderToShoulder #IRE #RWC2015

— David Patterson (@DPatz13) October 13, 2015

Who could forget one of his most inspirational moments in green...

A tribute …https://t.co/To8ZkAA9mh

— Gerard Meagher (@gerard_meagher) October 13, 2015

We’ll miss you, Paulie. Thanks for all the memories.