Here, RUCK looks at who is currently sidelined, doubtful and unavailable and why...
*this list will constantly be updated as injury news is released
IRELAND'S INJURED/UNAVAILABLE PLAYERS
LOCK
Tadhg Beirne (knee)
Iain Henderson (finger)
Devin Toner (ankle)
BACK ROW
Sean Reidy (hand)
Marcell Coetzee (hamstring)
CJ Stander (facial fracture)
Rhys Ruddock (Hamstring)
Dan Leavy (Calf)
SCRUM-HALF
Luke McGrath (knee)
Kieran Marmion (ankle)
FLY-HALF
Tyler Bleyendaal (neck)
Billy Burns (concussion)
CENTRE
Garry Ringrose (hamstring)
ENGLAND'S INJURED/UNAVAILABLE PLAYERS
Dylan Hartley of England (Capt) arrives before the six Nations Championship match, between England and Ireland at Twickenham Stadium, London , UK, on the 17th March 2017. (Photo:Dean Lancaster/PPAUK)
PROP
Beno Obano (knee)
Joe Marler (retired)
BACK ROW
Sam Simmonds (ACL)
Jack Willis (knee)
Sam Underhill (ankle)
Brad Shields (side strain)
CENTRE
Piers Francis (shoulder)
WING
Anthony Watson (Achilles)
Marland Yarde (knee)
Chris Ashton (ankle)
SCOTLAND'S INJURED/UNAVAILABLE PLAYERS
PROP
Zander Fagerson (ankle)
Jon Welsh (tbc)
HOOKER
Fraser Brown (knee)
George Turner (ankle)
LOCK
Richie Gray (back)
Lewis Carmichael (tbc)
BACK ROW
Hamish Watson (hand)
John Barclay (Achilles)
Blade Thomson (concussion)
David Denton (head)
Matt Fagerson (shoulder)
Magnus Bradbury (shoulder)
Luke Hamilton (shoulder)
Cornell Du Preez (throat)
Sam Skinnner (ankle)
John Hardie (knee)
Ryan Wilson
Fly-half
Finn Russell (Head)
George Horne (Shoulder)
CENTRE
Duncan Taylor (knee)
Mark Bennett (hamstring)
Matt Scott (concussion)
Huw Jones (knee)
WING
Lee Jones (Knee)
Damien Hoyland (tbc)
FULLBACK
Stuart Hogg (shoulder)
WALES' INJURED/UNAVAILABLE PLAYERS
PROP
Rhodri Jones (shoulder)
Nicky Smith (ankle)
Leon Brown (thumb)
LOCK
Jake Ball (shoulder)
Bradley Davies (knee)
BACK ROW
Ellis Jenkins (knee)
Aaron Shingler (ACL)
Taulupe Faletau (arm)
Dan Lydiate (bicep)
Ollie Griffiths (knee)
James Davies (foot)
SCRUM-HALF
Rhys Webb (ineligible)
FLY-HALF
Rhys Patchell (hamstring)
CENTRE
Scott Williams (hamstring)