IN the end it was elementary — but Wanderers’ passage into the fifth round of the FA Cup was not without its mysterious moments.

The rolling mists around the Reebok lent this game an air of Hound of the Baskervilles, but for the first half at least, it was a case of what had happened to the side that had stood toe-to-toe with Arsenal in successive Premier League games?

Wanderers seemed to struggle desperately with their tag of favourites, albeit marginal ones, having chased one of the best footballing sides on the planet for 180 lung-busting minutes in their previous two outings.

So, a dreary afternoon spent largely in the ascendancy came as somewhat of a culture shock, at least until Owen Coyle had chance to work his magic at the break.

Missing Gavin McCann, Mark Davies, Ricardo Gardner and Matt Taylor through injury — figuring out the Wanderers line-up must have been a mystery in itself for the manager, who opted to play Jlloyd Samuel in a very unfamiliar left midfield role, ahead of Sam Ricketts.

And on the bench, the appearance of forgotten man Riga was surprise enough, until you realised that Ricardo Vaz Te — whose last appearance was in September 2008 — was also present in the pre-match warm-up.

The curiosities also seemed to spread to the opposite camp, where Dutchman Marcel Seip had to be switched from Kevin Blackwell’s squad at the last minute after damaging his hamstring in the pre-match warm-up, to be replaced by Jonathan Fortune.

Wanderers looked disjointed from the start but did manage to carve out the game’s first decent chance on 18 minutes when Kevin Davies and Tamir Cohen conspired intelligently on the left to set up Ivan Klasnic, whose low shot was saved at the second attempt by Mark Bunn.

Briefly, the game sprung into life. Former Wigan striker Henri Camara should have scored after racing on to Lee Williamson’s pass and lifting the ball over Jussi Jaaskelainen, only for it to drop the wrong side of the crossbar.

That proved to be the Blades’ best chance of the game — but at the other end, makeshift winger Samuel found himself in nosebleed territory as he danced around Chris Morgan to fashion an excellent goal-scoring opportunity, only to try his luck again and allow the defender to clear.

The full-back hasn’t scored for nearly six years, and had he taken the chance on earlier, might have ended his drought in spectacular style.

From that moment on, the game reverted to anonymity, punctuated only by the odd Sheffield United set piece flashed across the face of goal. On one such occasion, Morgan might have caught Gary Cahill napping at the far post, but otherwise Wanderers — and the outstanding Zat Knight in particular — were rarely shaken out of their comfort zone.

Just before the break, Chung-Yong Lee finally got the possession he had enjoyed so much against Arsenal, fashioning a string of half chances in stoppage time.

Cahill cleared the bar with a header from the edge of the box, and the South Korea international also laid on an opportunity for Ivan Klasnic, who uncharacteristically failed to get a good connection in the penalty area.

It had been disjoined fayre from the Whites, but Coyle sent his side out with the instruction to get the ball immediately wide to Chung-Yong, and within three minutes was celebrating a goal.

The winger combined with Davies to play Gretar Steinsson in on the right, and while the full-back looked odds on to cross the ball, he somehow found a gap to squeeze his shot past Bunn from the angle to register his first strike since the penultimate game of last season against Hull City.

Blackwell threw on two more strikers in Jamie Ward and Richard Cresswell to try to get his side back into the game, but the Blades’ general lack of guile prevented them from ever really putting any doubt in Wanderers’ minds once they had gone ahead. And any lingering fears were put to bed when Johan Elmander came off the bench to score the second six minutes from time.

Chung-Yong played a perfectly timed pass down the right to send the Sweden international through on goal, and while the angle again looked daunting, he showed impressive composure to drill his shot just inside the far post.

Elmander might have grabbed a second late on after a mistake from Kyle Walker but chose to take his shot too early and hit only the side netting.

But the 28-year-old’s goalscoring return was a welcome one, and he might well have done enough to convince his manager that he is worth a start against Burnley tomorrow night.

That game, of course, will provide the real acid test for Coyle’s embryonic Wanderers team, and they will almost certainly have to click into gear quicker than they did before the mists cleared in the FA Cup.

We are all still searching for clues as to how the new boss will go about the business of getting Wanderers clear of the relegation race — which, of course, is his main priority.

But there’s no disguising the fact that with Manchester United and Liverpool already out — the diminished sign of the big four in this year’s competition makes for encouraging reading.