In the modern game, with the high level of attrition and injury, you never know when your chance is going to come.
For Sam Underhill, it came on Saturday.
Without flanker Tom Curry's ankle injury, I think he would have started against Japan this autumn and got some minutes as a replacement in the other three matches.
Instead, he was released on New Zealand and pushed himself to the front of the queue as England's first-choice open-side flanker.
He topped the game's tackle count by a distance, with 24, and was England's joint-top metre-maker, matched only by wing Jonny May.
|England v New Zealand player statistics|
|Tackles made||Metres made|
|Sam Underhilll (Eng) 24||Ben Smith (NZ) 74|
|Maro Itoje (Eng) 20||Jonny May (Eng) 66|
|Mark Wilson (Eng) 17||Sam Underhill (Eng) 66|
|George Kruis (Eng) 14||Damian McKenzie (NZ) 57|
He also supplied Twickenham with a moment that will live long in the memory, even if it ultimately counted for nothing.
When he collected Courtney Lawes' charge-down in the 75th minute and burst towards the All Blacks line, he seemed to be covered by Beauden Barrett.
This time last year, the New Zealand fly-half produced a superb recovery tackle to deny the far quicker Stuart Hogg as the Scotland full-back headed for the corner in the final play of a narrow 22-17 win at Murrayfield.
But Underhill produced a remarkable 'in-out' swerve to leave the reigning World Player of the Year chasing his tail.
It would have been a try worthy of winning a game against the best side in the world. but Lawes was at least half a metre offside and it was the correct decision from referee Jerome Garces to rule out the score.
The thing about Underhill though is that he could be so much more.
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He has to establish himself as more than a pure tackler.
That is the first skill you are taught in mini rugby and, while Underhill has taken it to another level, it is very hard to make that your point of difference.
Occasionally it can be a match-winning quality.
In England's 12-6 win over Wales in the Six Nations in February, Underhill produced a superb try-saving tackle on Scott Williams, rolling the centre into touch as he seemed poised to score.
But those sort of heroics are one-offs rather than a way of regularly deciding games.
Turnovers are the really valuable currency for an open-side flanker. Those, together with minimising errors and penalties against you, are the way to deny the opposition a chance of momentum and strangle the life out of the contest.
Australia back row David Pocock is the archetype. During the last World Cup, he secured a tournament-high total of 17 turnovers across five-and-a-half games, including three in the final.
Curry, Underhill's main rival for the England seven shirt, averaged three a match for Sale last season.
Making 20 tackles a match does not make you indispensible in the same way.
That huge work-rate is commendable, but it comes at the cost of Underhill being effective at the breakdown.
Too often he is the man on the floor, rather than next on the scene, jackalling over the top to slow up and steal opposition ball or secure his team's own.
His carrying is solid, but not exceptional. In the first minute, he was stripped of possession by Sam Whitelock. The very best don't allow that to happen to them.
He has the powerful build and low centre of gravity to be immoveable over the ball.
From what I have seen of him at Bath, he is very analytical about his performances and relishes the chance to disrupt the opposition.
His performance on Saturday must have made him England's first-choice open-side flanker, but he has to change his game if he is to be a genuine seven rather than another of the "six-and-a-halves" that Eddie Jones has made do with in his back row.
Fast feet from Little Mac give England defence food for thought
While Underhill operates in close quarters, it was New Zealand full-back Damian McKenzie who shone in broken field at Twickenham.
We should be careful. This was only his 14th Test start and he has taken his time to nail down his place ahead of Jordie Barrett and others. But, when coach Steve Hansen shunts a world-class full-back like Ben Smith out to the wing to accommodate McKenzie, you know he is a great talent.
There was one sequence early in the first half which showed his innate feeling for space and startling acceleration.
New Zealand were caught short-staffed in the backfield after Ardie Savea was superbly stripped of possession in England's 22m by Owen Farrell and Ben Youngs took the chance to kick deep.
It is that sort of elusive, mazy running that prompted Hansen to describe McKenzie as "a fly in a bottle" last year.
He seems to have a sixth sense for where tacklers are coming from and how to use their momentum against them, particularly on greasy surfaces like a sodden Twickenham.
Many people say rugby is about size and power nowadays, but he has the speed and skills to make an impression without either of those.
In a sport that is so often focused on winning the collision, it also takes a bravery, composure and nerve to sacrifice forward momentum for those lateral side-steps.
He showed a different skill-set for his try, piercing the England defence with raw speed and an eye for a gap rather than dazzling one-on-one footwork.
Next weekend will be interesting for McKenzie.
At 5ft 10in tall, he is an obvious target for Ireland to try and exploit with their aerial game.
I could see Ireland coach Joe Schmidt conjuring some pre-planned ploy that attempts to occupy Ben Smith elsewhere and isolate McKenzie under a high ball with either Robbie Henshaw (6ft 3in) or Jacob Stockdale (6ft 4in) for company.
But the All Blacks will be ready for that and have their contingencies in place.
Jeremy Guscott was speaking to BBC Sport's Mike Henson.