Stuart Gray pin-pointed Derby wide man Patrick Bamford beforehand as a quality player who can score goals - and the Wednesday boss was proved right last night in stunning fashion.
A marvellous strike by the on-loan 20-year-old from Chelsea sent the Owls slipping to a second successive defeat and was the only difference between them and the promotion-hunting Rams.
A new-look Wednesday side matched the loftily-placed visitors in every other respect in an absorbing and even contest of few chances, which was marred only by some poor refereeing..
It was Bamford’s fifth goal in his last sixth games and his 22nd of the season - the others came when he was on loan at MK Dons.
He struck in the 78th minute: around 20 yards out, on the right, near the outer corner of the Leppings Lane box, he whipped a brilliant left-foot shot that gave Chris Kirkland not a prayer as it flew in off the underside of the bar.
It was not the only blow for Wednesday: Kieran Lee went off just before half time with what appeared to be a worrying injury, a week after his usual midfield partner Jose Semedo was carried off.
Lee, the Owls’ January Player of the Month, hurt himself near the right-side corner flag at the Leppings Lane End.
Soon afterwards he went down in the centre circle, in the 44th minute.
It was soon obvious that the problem was not minor: he walked very slowly from the field, accompanied by physio Paul Smith, in the first minute of first-half stoppage time, though only three extra minutes had been announced.
Jeremy Helan had to sent into central midfield to see out the half. Gray had also spoken with almost envy of the fact that Steve McClaren had avoided long-term injuries in his squad and had been able to field a settled side.
The evidence was there again as the former England boss named the same team that beat QPR 1-0 eight days earlier, with Jamie Ward fit despite having had to go off in that game with a hamstring problem.
But Gray made five changes to the line-up that started last week’s 3-0 defeat by Wigan.
He gave a third Wednesday ‘debut’ to Leon Best and a first start to Gary Gardner; recalled Giles Coke after his three-match ban and Glenn Loovens after his recovery from hamstring trouble, and handed Michail Antonio the first start of his comeback after a knee injury.
The Owls were without Semedo, who suffered severe ankle damage last week, while Benik Afobe, Jacques Maghoma and Atdhe Nuhiu were dropped to the bench and Adedeji Oshilaja was left out altogether.
New boy Sam Hutchinson was among the subs.
This fresh Wednesday side showed a tactical variation as well.
It was virtually 4-2-3-1 at the start, with Kieran Lee and Giles Coke the deepest of the midfield men. Antonio and Chris Maguire were on the left and right respectively, and Gardner was playing not far behind Best, the lone striker.
The plan will have been partly influenced by Gray’s high regard for Derby’s midfield strength. The Rams as usual had Chris Martin mostly on his own up front.
But Wednesday had not come with defence uppermost in their minds: they attacked the ne end where the upper tier was almost filled by Rams fans - and with Antonio an immediate threat his powerful run won a corner, taken by Maguire, headed down by Loovens and cleared off the line.
Gardner’s forward role also meant him occupying midfielder John Eustace, who was in his normal role in front of the back four.
The play was largely cagey in the first 25 minutes and there was nothing to choose between the two sides - a compliment to the Owls when they were up against a top-four side.
There was also nothing to get the crowd over-excited - but the home fans yelled in vain for a penalty when Antonio angled a fine ball into the box and Best and centre half Richard Keogh went down in a tangle. Best thought it was a foul, as well
The first real danger to Wednesday came when Will Hughes cut inside on his left foot and had ex-United forward Jamie Ward unmarked to his left. Hughes shot tamely at Chris Kirkland rather than pass, and Ward showed his displeasure.
Ward - getting some stick from home fans - guided a cross from which Patrick Bamford, on loan from Chelsea, sent a diving header wide; Miguel Llera was similarly off target from a Maguire free kick.
The second half began the same way as the first - with Derby saved by a goal-line clearance, this time by midfielder Craig Bryson as he stopped a Maguire corner from going straight in.
Antonio continued to be the main threat for the Owls and a shot on the turn from 20 yards was pushed wide by ex-Owls keeper Lee Grant, who also did well to catch another well-struck effort from the winger.
Gardner had made a favourable impression but Gray sent on the fresh legs of Hutchinson, who quickly made his mark with a perfectly timed tackle in the Owls box.
Hutchinson was in central midfield: Helan went wide on the left, Antonio switched to the right and Maguire was now up front with Best, until the latter was replaced by Afobe.
Bamford’s goal broke the stalemate, and Derby held firm.