How long do you keep the faith in an under-performing player?

Rugby is an all-consuming passion of mine but every so often another sport takes precedence for a while.

If it were a choice between watching New Zealand play in the cavernous MCG – so big it dwarfs the Great Barrier Reef from space – this Sunday or the Canterbury Crusaders, then it’d be my best wishes to the Crusaders against the Bulls and all eyes would be on the Black Caps’ quest for glory.

However, watching the unsung heroes of Martin Guptill and Grant Elliott perform well above expectations in the knockout rounds – low as they were – I can’t help but draw parallels with rugby.

Both these players had been in a form slump, and their place in the side had been questioned. The big names – not MCG big, more like L&P big, as in world famous in New Zealand big – like Kane Williamson, Trent Boult and Brendon McCullum had stepped up in the early matches and Guptill and Elliott were the equivalent of navel flint. Everybody knew they were there, but nobody quite knew how.

It is an extremely difficult question that all selectors must ask: how much faith do you place in a player who isn’t performing to expectations, and how many opportunities do you give them?

Last year, Danny Care made a comeback that would’ve made Elvis blush. This year the focus has been on the rise of Rhys Webb for Wales and the growing figurative stature of Conor Murray. Against France, to his great credit, Care was sporting enough to tweet that he wished he were playing but his replacement, Ben Youngs, was playing like an Alicia Keys song.

Youngs made a dazzling debut against Australia in 2010 as a 20-year-old, and set up that length-of-the-field try for Chris Ashton later that year. Since then he has fallen out of favour. England versus France gave him the chance to shine again.

The question is, much like what to do with Owen Farrell when he returns from injury, in whom does Stuart Lancaster place his faith?

Depth is a good thing to have and some rotation is required, but deep down you have to know who your best starting team is. I have the sneaking suspicion that Lancaster does not know what his best side is, simply because injury and form have robbed him of continuity in selections.

This dilemma is not unique to the European teams. Australia, noticeably in the forwards, soar and descend into the darkness like the Space Mountain roller-coaster at Disneyland.

Compare the performance at Eden Park last year with the Newlands Test. The forwards in the former played like the turnstiles to go on Space Mountain, then in the latter largely resembled the adrenaline rush after the ride.

Scott Higganbotham, Wycliff Palu, Sam Carter and Will Skelton are examples of cats with nine lives. But much like Kurtley Beale, just when you thought they’d used up their ninth, they were allowed to extend their bar tab at The Last Chance Saloon.

For South Africa, there was the problem of experienced players and fringe players. Captain Jean de Villiers was noticeably off the pace in terms of form, and Victor Matfield is still a lineout god but a mere mortal at the breakdown. Handré Pollard and Patrick Lambie prevented Morné Steyn from taking the ground but, like Sauron, while he cannot yet take physical form his evil shadow lurks.

Similarly, Bismarck du Plessis had, by his standards, a year to forget in 2014. He was arguably overplayed in the Sharks and never recovered the form that made him an automatic choice for hooker in people’s World XV lists. Heyneke Meyer tried starting him and then coming off the bench. Neither worked.

Much like the battle between Israel Dagg and Ben Smith at fullback, there was no clear winner between Adriaan Strauss and Bismarck, in that both were down on form, or at least on impact from the previous year.

With experienced players, however, there is more leeway given. The problem is starting off your career and taking the chances you’re given, or showing enough potential to justify your continued selection.

Sam Cane, Victor Vito and Colin Slade, all had sketchy starts to their careers for New Zealand.

Cane was not considered physical enough until his Eden Park awakening, where he acted out RoboCop with a swathe of bandages.

Vito was incorrectly chosen as a 6 early on and suffered accordingly. Much like his more illustrious teammate Jerome Kaino, there were calls early on for his axing.

Slade had a horror run of injuries and didn’t look like he was enjoying his rugby after his promising Sydney debut. With the poor goal kicking of Aaron Cruden and Beauden Barrett last year, there couldn’t have been a better player to kick that winning conversion in Brisbane.

Some players have had to fight tooth and nail to get back into the squad, whereas others have been messed around positionally or dumped unceremoniously.

Francis Saili seems to have had his chance and blown it, whereas someone like Malakai Fekitoa has done enough to stay in the picture. Is that a fair reflection of their talents?

Declan Kidney gave Luke Fitzgerald and Shane O’Leary a raft of chances before excluding them from his 2011 World Cup squad, preferring to place his faith in the experience of Gordon D’Arcy.

Players like James Hook have moved around more than a hermit crab, and let’s see if Israel Folau lines up for the Wallabies at outside centre this year or whether he stays at fullback where he suffered a mini points drought.

In the end, you drive yourself crazy thinking about what might have been if other players had joined the fold. Like characters in a movie trying to explain time travel, thinking about what might have been or could be gives you a headache; all you can do is concentrate on the players you have and how they perform.

When somebody who hasn’t been performing puts in a standout performance, the pressure is taken off to some extent and applied even more in another. Sometimes an amazing performance can be a curse, as it becomes a new standard.

Fans are generally as fickle as they come, so players do well to even dare approach their impossible demands. Instead of celebrating these brilliant performances, there is the temptation to feel short-changed about the players’ career. Why haven’t we seen him perform like that before?

To use a cricketing analogy, it would be far more realistic to tell our rugby players in these instances this is what you’re capable of when everything goes right so let’s see if you can improve your average a little when everything doesn’t click.