It's regularly pointed out that players who have missed out on being selected in the initial British and Irish Lions squad needn't give up hope.
The tours are gruelling and there are, unfortunately, always injuries along the way and replacements will get the call for reinforcements.
The class of 2017 will face one of the most demanding schedules in modern times, lining up against four Super Rugby sides, as well as the New Zealand Provincial Barbarians and the Maori.
And that's before we even get to the first Test.
Then there's the three-Test series itself, with a game against the high-flying Hurricanes sandwiched in between the first and second instalment.
On April 19, the likes of Jamie Roberts, Finn Russell, Mike Brown and Dylan Hartley were left disappointed by their relative snubs.
But all is not lost.
Alex Corbisiero, who knows a thing or two about call-ups, advised that they all train as if they're going on the tour and be prepared for the SOS.
Last time out there were nine players who initially missed out but were then called down to Australia during the tour.
Here are the players who received the call from Warren Gatland four years ago...
Rory Best (for Dylan Hartley - May 26)
A bit of a strange one, Best was actually called into the squad on May 26, before they left for Hong Kong. But still technically a call-up.
England hooker Dylan Hartley, who had been named and collected his kit ahead of the tour, was then banned for verbally abusing referee Wayne Barnes during the Aviva Premiership final.
Hartley had the option to appeal the ban, but the Lions had no choice but to call up a replacement.
The Irishman went on to make four appearances but didn't feature in the Test series, though he did captain the side against the Brumbies.
Alex Corbisiero (for Cian Healy - June 5)
Ireland prop Healy suffered significant ligament damage when he rolled his ankle during the Lions' second match of the tour against the Western Force.
Gatland immediately sent for Corbisiero even before the extent of Healy's injury was clear.
Eventually the Irishman was sent home from the tour and Corbisiero went on to play in three tour matches plus two of the Test matches, scoring the opening try in the decisive third Test.
Ryan Grant (for Gethin Jenkins - June 7)
Gethin Jenkins' calf problems refused to subside, leaving Warren Gatland staring at a prop crisis, particularly when it came to loose-heads.
It had been hoped Jenkins would overcome the problem and was named to start against the Queensland Reds, but had to withdraw from that fixture.
He was eventually sent home without seeing any action and Grant was summoned from Scotland's tour of South Africa.
Grant went on to play in three tour matches and was an unused substitute in the second Test.
Simon Zebo (Cover for Tommy Bowe - June 9)
Bowe required minor surgery to repair a broken bone in his hand but remained on the tour with medical staff confident he would recover in time to feature once again later in the tour.
But in the meantime, Zebo was called from Ireland's tour of the USA and was required as cover in Australia whilst his compatriot was sidelined.
Bowe, whose only try of the tour came against the Western Force, would indeed go on to recover from his injury and started the final two Tests during the series win.
Zebo, on the other hand, played in three games against Super Rugby sides but didn't score.
Billy Twelvetrees (Backline cover - June 12)
The versatile play-maker was summoned from England's tour of Argentina with a trio of Lions players out with niggles.
Fly-halves Johnny Sexton and Owen Farrell both had hamstring problems and centre Manu Tuilagi suffered a stinger during the Lions' hard-fought win over the Reds.
Both No.10s recovered from their injuries to play key roles in the tour but Tuilagi was only good for one further run-out, against the Rebels.
Despite all three players remaining on tour, Twelvetrees did manage to get two appearance against Super Rugby sides but wasn't near the Test team.
Christian Wade, Brad Barritt and Shane Williams (Backline cover - June 15)
The Lions had a number of players receiving 'ongoing treatment' and reinforcements were required for the midweek matches.
Jamie Roberts had a hamstring problem that would see him miss a large chunk of the tour and George North was also receiving treatment.
Williams' call-up came as a real shock and the fact he was playing in Japan at the time went a long way to him receiving the call. It meant they could get him to Australia faster than most.
He was only required for the one game.
Wasps speedster Wade was called up after impressing during England's opening tour match against Argentina, whilst Barritt was, who was rested for that tour, was on holiday in the US.
Wade's only involvement in the tour was the Lions' 14-12 defeat to the Brumbies, which took place three days after his call-up.
Barritt also started that game but went on to face the Melbourne Rebels as well.
Tom Court (cover for Alex Corbisiero - June 23)
The Englishman suffered a calf strain during the first Test victory over the Wallabies and suddenly the Lions were light in the front row.
A final midweek game - between the first and second Test - beckoned and it was a case of right time and right place for the Irishman.
Court was on holiday in Australia and before he knew it, he was on the bench for the Lions as they took on the Melbourne Rebels.
He came on in the 55th minute of the match, which was over as a contest at that point, but those 25 minutes were his only involvement in the tour.
