The Owls edged closer to the start of the new campaign with a 4-2 reverse at League One outfit Scunthorpe.
An entertaining encounter saw Wednesday twice go in front through Atdhe Nuhiu and Marco Matias but Paddy Madden (2), Kevin van Veen and Kyle Wootton struck for the Iron to make the difference.
Wednesday now take on Scottish side St Mirren at Hillsborough next Saturday before the Championship curtain-raiser against Bristol City seven days later.
The Iron contest saw a strong start for the Owls, who fashioned an early shot on goal with Ross Wallace teeing up Nuhiu, whose shot was deflected wide.
And from the resulting corner on 12 minutes - and the same combination - Wednesday took the lead.
Wallace sent over an accurate flag kick and Nuhiu climbed high to nod home with keeper Luke Daniels stranded.
But the advantage was surrendered in little over a minute as van Veen broke free down the right and drilled low into the box for Madden to net from close range.
On 21 minutes, though, the pendulum swung back into Wednesday’s favour. A mix-up in the Scunthorpe defence allowed Nuhiu to feed Matias and the Portuguese tapped into an unguarded goal.
A minute later, the earlier pattern was almost repeated. Madden motored down the right this time and crossed for Tom Hopper, who came within a whisker of converting.
But Madden himself made no mistake on 26 minutes. Scott Laird aimed a teasing delivery into the danger zone and the lively striker smashed in a fierce volley from six yards.
The Iron started the second half with intent and Laird burst forward before hitting hard and low down the throat of Keiren Westwood.
Liam Palmer then denied the lively Madden a hat-trick with a timely intervention on the line but Scunthorpe pressed and on 68 minutes made it 3-2 when van Veen arrowed in on goal and unleashed an accurate effort that flew past Westwood.
The Owls went in search of an equaliser and had a penalty appeal turned down when Nuhiu went sprawling in the box and the same player just missed out on a Caolan Lavery cross ten minutes from time.
But Scunthorpe broke and applied the final coating of gloss on 89 minutes when Jordan Clarke crossed for Wootton to head home at the far post.
Owls: Westwood (Price 69), Palmer (Hunt 64), Loovens, Lees, Helan, Wallace (May 64), Semedo (Lavery 70), McGugan (Hutchinson 64), Lopez (Lee 64), Matias, Nuhiu