The squads of international rugby teams boast stellar talent when fully fit, but sadly injuries are part of the game.
Through bad luck or collisions, every player is bound to pick them up at some stage during their respective careers.
With this, we pick our best XV who will be unavailable for large spells of the upcoming Six Nations whether through injury or suspension.
15. Jared Payne (Ireland)
The Ulster and Ireland centre-cum-full back has not played any rugby since suffering a head injury during the Lions tour of New Zealand in July.
The 32-year-old has been suffering with severe headaches since returning to pre-season in September and has been receiving constant medical attention – with no return date in sight by Ulster coach Les Kiss.
Solid in the tackle and always a threat going forward, the Kiwi-born star is a major force for Ireland alongside Rob Henshaw in the middle and will be a loss for the Six Nations.
Payne gives Joe Schmidt’s side a lot of ball on the front foot and has the ability to threaten opposition defences with and without the ball.
14. Elliot Daly (England)
The cultured winger damaged his ankle during Wasps’ 21-3 win over La Rochelle in the Champions Cup last month.
Although he does not require surgery, the Lions man is set to be out for up to three months.
His loss will be significant to Eddie Jones – not just due to his versatility – but he was also a key man for England during the Autumn Internationals, scoring tries against Samoa (two) and Australia.
With Jonny May, Anthony Watson and Jack Nowell available for selection, Jones has decent cover as his side bid for a third consecutive Six Nations title.
13. Jonathan Davies (Wales)
Labelled as one of the best centres in the world following his man-of-the-match displays for the Lions in New Zealand, Davies’ absence is a major blow to Wales.
The 29-year-old suffered a horror ankle injury during the final minutes of November’s 29-21 defeat to Australia in Cardiff – and is set to be out for six months.
The Scarlets star has been a constant source of inspiration for Warren Gatland’s side and his work in the wider channels is always a major threat.
12. Wesley Fofana (France)
The barreling France centre, who had only just returned after a nine-month absence from injury, is ruled out again for three months due to a neck injury.
The 29-year-old, with 44 caps to his name, will undergo surgery this month but could return for the penultimate stages of Clermont's Champions Cup campaign in April.
Fofana has a knack for catching opposition attackers behind the gain line and, coupled with his strong offloading ability, is a superb asset to any starting line-up.
His loss will be a devastating blow to new French coach Jacques Brune - with Mathieu Bastareaud now tasked with leading the midfield for Les Bleus.
11. Angelo Esposito (Italy)
One of the leading lights of the Italian back line, Esposito sustained an anterior cruciate ligament injury last month and is ruled out for the rest of the season.
The 24-year-old had been in instrumental form this term, scoring two tries against Zebre in December before limping off with a knee injury.
The Treviso flyer has registered two tries in 15 appearances for the Azzurri, and remains a key part of Conor O’Shea’s.
10. Camille Lopez (France)
The fly-half is out for a substantial spell after suffering a leg fracture against Northampton in October.
His club Clermont have given no time-frame for his recovery, but he looks certain to be sidelined until the latter end of the season - with Toulon youngster Anthony Belleau set to be handed the coveted 10 shirt for the Six Nations.
Although France have struggled of late, Lopez's ability to eye gaps and deliver cleverly-weighted passes has seen him evolve into one of Les Bleus' influential figures.
9. Greig Laidlaw (Scotland)
While Laidlaw is expected to return to action at some point during the tournament, there is no guarantee he will be match fit after spending the last three months on the sidelines with a broken fibula.
One of the central figures of a burgeoning Scotland team, Laidlaw offers terrific pace around the base of the scrum and has the ability to bring players into the game from any attack.
His current spell at Clermont will have certainly improved his game - and at 32 - has the chance to further inspire Scotland in the lead up to the 2019 Rugby World Cup.
1. Joe Marler (England)
The Harlequins loose-head will miss England's matches against Italy and Wales after receiving a six-week suspension for striking with the shoulder against Sale earlier this month.
Although he is free to play from February 20, it will be interesting to see whether Jones selects him considering the duration he will spend on the sidelines.
His carrying and work at the breakdown will be a significant loss - and coupled with other front row injures - Mako Vunipola will be the only fit loose-head for the Red Rose's key early fixtures.
2. Ross Ford (Scotland)
Scotland's most capped player will miss the Six Nations after picking up a pectoral injury in November.
At 33, the Edinburgh star has over 13 years experience on the international stage and his ability to stabilise the line-out will be greatly missed.
A crucial part of Gregor Townsend's side, his loss will be a crushing blow with limited options available in the front row.
3. WP Nel (Scotland)
Destructive WP Nel is out until April with a broken arm - picked up in Scotland's win over Samoa in November.
The 31-year-old will be a major loss to Scotland after showing glimpses of his outstanding ability over the last two seasons.
Newcastle's Jon Welsh - with just 11 caps - has the chance to step up and show his class this Spring.
4. Jake Ball (Wales)
The totemic Wales lock is a long-term casualty after dislocating his shoulder in Wales' defeat to New Zealand in November.
The 26-year-old, with 28 caps, is a towering line-out presence and his voracious work-rate has made him one of Gatland's key men.
Although he boasts nothing near the influence of Alun Wyn-Jones, the Scarlets player puts his body on the line and epitomises the warrior spirit of the Wales pack.
5. James King (Wales)
The Ospreys lock-cum-back-row forward may have only featured for Wales just once in 2017 but injuries have somewhat curtailed his steady development as a player.
The 27-year-old suffered a shoulder injury in his side's win over Northampton last month and will miss the next five weeks.
A hard worker in defence and a menace at the breakdown, the Cardiff native has the potential to be the bedrock of the Wales line-out when Wyn-Jones and Bradley Davies retire.
6. Taulupe Faletau (Wales)
The abrasive Faletau twisted his knee in Bath's Champions Cup defeat to Toulon last month and will miss the entire Six Nations.
The 27-year-old has had previous trouble with the same knee - having injured it on his Premiership debut for Bath last season.
His ball carrying and restart work make him one of the most dangerous forwards around - and his consistent performances are always a positive to how Bath or Wales perform.
A menace around the breakdown, his absence will be another huge blow to Gatland's hopes of success.
7. Sam Warburton (Wales)
The Wales and Lions captain has been ruled out for the rest of the season after having knee surgery.
While he was already sidelined with a neck problem, the 29-year-old is likely to be out for up to six months.
It was initially hoped that Warburton would be fit for Cardiff's January fixtures in a bid to boost his match sharpness for the Six Nations, however, the proposed surgery was planned to give him the best chance of being injury-free in the build up to next summer's World Cup.
If Gatland’s men are to have a successful campaign in Japan, then Warburton is one of the marquee names they’ll be looking towards for innovation and leadership.
8. Billy Vunipola (England)
Another mammoth blow to Jones' side as Billy Vunipola is to miss the Six Nations after fracturing his forearm during Saracens draw against Ospreys on Sunday.
The talisman No8 had just returned from a three-month absence with knee trouble, with the 15-15 draw against Ospreys only his second match since coming back from injury.
Vunipola's absence deepens England's back-row crisis - with Exeter's Sam Simmonds expected to get the nod, having only made his debut in November.