IT MIGHT not seem like a big deal, but switching from right centre-back to left isn’t as simple as shifting along a few yards and doing the same things.

Your starting position is different for every action, the way you shape up to receive the ball is a mirror image of what you’re used to. Releasing it, too, can be slightly more awkward depending on where you’re passing it.

Tackling, blocking, stepping off, dropping in… the angles just aren’t the same. Things don’t really flow quite as instinctively.

That’s what 21-year-old Stephen Welsh faced in Wednesday night’s Europa League qualifying play-off first leg against AZ Alkmaar – and he embraced it all with quite remarkable confidence.

READ MORE: Celtic's exposed right flank and the Carl Starfelt concern amid five AZ chances

In an era when centre-backs are expected to actively contribute to build-up play by breaking lines and starting moves, switching sides for a big game would make it easy to become slightly flustered, to allow yourself to drown in indecision by taking that extra split second too long to consider every action.

That’s especially risky in a system such as Ange Postecoglou’s, where quick, decisive actions are required at every juncture in the constant quest to create space, beat the opposition press and keep up your own attacking tempo.

Yes, Postecoglou had Welsh spend some minutes at left centre-back in a couple of the team’s pre-season friendlies but it’s hardly the same – both in level of opposition and intensity – particularly when he’s still relatively inexperienced on the right at senior level never mind left.

Celtic Way:

Yet the stats paint a pretty vivid picture of someone who didn’t just tread water when he was thrown in, but who was already wearing his goggles and cap in preparation for the splash.

Welsh’s area of the pitch saw some of the most intense passages of play in the most even match – in terms of possession anyway – that Celtic have been involved in since Postecoglou took over yet he emerged with virtually no blots on his copybook.

Instead, Welsh surfaced with game-high numbers in total successful actions (86), recoveries (18), successful passes (70), defensive duel percentage (100 per cent), clearances (six) and interceptions (16).

Added to these, he led the Celtic players in passing percentage (93 per cent) and duel win percentage (71 per cent).

Celtic Way:

Naturally, Welsh’s defensive partner Carl Starfelt also switched sides against AZ.

The Swede, 26, has been playing left centre-back since joining the Hoops last month and was moved back to the right-sided berth he favoured while with IFK Goteborg in his homeland and during his initial time with his last club, Rubin Kazan of Russia.

Despite the duels fought on Celtic’s left half-space and left flank, AZ clearly got more joy down the right on Wednesday when it came to actually managing to breach the Hoops defence and create scoring opportunities.

While not solely at fault for AZ’s relative success in those areas, Starfelt’s stray passes, missed interceptions and generally quite shaky demeanour stick in the mind as times when the more experienced of Celtic’s central defensive duo looked the one in need of some water-wings.

Indeed, more than once Welsh was forced to come across to cover for Starfelt with pressures, tackles and blocks and he did it all with the same gusto as he approached his own work on the left.

Celtic Way: Welsh's total actions map v AZWelsh's total actions map v AZ

Of course, as some of you will no doubt be thinking, plenty of right-footers play left of centre. Some even prefer it; Sergio Ramos and Virgil van Dijk spring to mind straight away as two top-tier examples of defenders who operate on the “wrong” side.

That’s not really the point here, though. Nobody’s arguing that it’s such a rare sight in and of itself, simply that it’s worth acknowledging Welsh’s extraordinary display when faced with making that shift in an important match.

The fact he was accompanied by a more experienced, but also more unsteady, defensive partner just reinforces how impressively the young Celtic centre-back performed.

Welsh swam so strongly when he was thrown into unfamiliar waters against AZ, who’d bet against him going on to create some more waves as the season progresses?