Ireland's centre-half partnerships in last 12 months tells its own story
There's a popular theory that a settled back four is essential if any side is going to be successful.
Martin O'Neill's Ireland have tested it.
Sunday's World Cup qualifier with Austria is Ireland's 10-competitive game in a 12-month window. O'Neill has used four starting centre-halves in that window: John O'Shea, Ciaran Clark, Shane Duffy and Richard Keogh.
They split duties at the Euros, when the latter pair benefited from a halfway reshuffle, and that trend has continued into the World Cup campaign. Injuries and suspensions have also contributed to the chopping and changing.
The tally of starts tells a story. Clark and Duffy are on five apiece; O'Shea and Keogh are on four. That is perhaps a reflection of the pecking order.
In the autumn there was marginal preference for the younger pair, who started three matches on the trot. But they were both ruled out of March's game with Wales, where the more experienced duo did a steady job
Clark's unavailability for this gathering means that the manager basically has to turn three into two, although he does have a variety of other options available.
The reality, though, is that Kevin Long, Andy Boyle and John Egan are options for the longer term, while Alex Pearce has been incapable of graduating beyond the periphery. Paul McShane missed out on the call after a long season with Reading ended on a sour note.
And three days out from Austria, it appears to be a straight choice between O'Shea and Keogh, with Duffy seemingly O'Neill's main man.
For Derby defender Keogh, who suffered a tough night against Mexico last week which he started in a three-man back-line and ended at right-full, the uncertainty is a familiar feeling.
"We have a very good group of players, there's going to be times when you play and others when you don't," says Keogh.
The manager has shown he's willing to make big decisions in big games at crucial times. He is that experienced and had a great career so he will make the right decision for Austria.
"As a player, you've got to keep yourself professional. I think it (the battle) is great but as a professional, you back yourself to play don't you? You have to prove that. I am no different.
"I don't care about competition; I've had that throughout my career and I have worked for everything I have got. When you're in the squad, you back yourself to play."
The change in the defensive picture for this game has moved beyond the heart of the back four. With Stephen Ward and Robbie Brady mixing it up on the left side - although Brady is now being deployed further up the park - the one constant was Seamus Coleman at right-full.
His unavailability for the remainder of the campaign has opened up the door to Keogh's clubmate Cyrus Christie, and the veteran has full confidence in his colleague.
"I have played with Cyrus at Coventry and Derby so it's great to see him come through and play so well," he continues. "It was a big blow for us to lose Seamus as he's such a brilliant player, a brilliant person and captain.
"For any team losing a player of that calibre would be tough, but when Cyrus has played, he's more than capable and it was nice for him to pop up with a goal against Uruguay."
Coleman will be coming in to join the Irish squad today and provide some words of encouragement building up to the weekend.
The team will be taking it easy today after yesterday's open training session at the Aviva Stadium, with O'Neill always keen to try and replicate the flow of a regular week at club level, where a day off halfway through is customary; for a Sunday game it tends to be Thursday.
Ireland's chosen centre-halves will not have to cope with Austrian attacker Marc Janko, who has been ruled out due to a bout of tonsilitis. Janko - who has just signed for Sparta Prague - started last November's game in Vienna and missed a gilt-edged late chance to equalise.
He has been replaced by Graz's Deni Alar, with coach Marcel Koller down a number of bodies - Stoke City's Marko Arnautovic is the highest-profile absentee.
Ireland's main striker Jonathan Walters sat out proceedings at the Aviva but there is no concern in the camp, with the Stoke man undergoing some gym work as part of his normal schedule in a season that has been interrupted by injury problems.
Centre-half partnerships since June 2016
Euro 2016 v Sweden: O’Shea, Clark
Euro 2016 v Belgium: O’Shea, Clark
Euro 2016 v Italy: Keogh, Duffy
Euro 2016 v France: Keogh, Duffy
WCQ v Serbia: O’Shea, Keogh
WCQ v Georgia: Duffy, Clark
WCQ v Moldova: Duffy, Clark
WCQ v Austria: Duffy, Clark
WCQ v Wales: O’Shea, Keogh
(Competitive games only)