Wednesday went down 2-1 to a resolute Brighton at Hillsborough, with goals either side of half time from Sam Baldock and Anthony Knockaert proving decisive.
Gary Hooper bagged a late consolation but it was too little too late for the hosts, who suffered a rare S6 defeat.
The Seagulls meanwhile, who missed out on automatic promotion last season by a solitary strike, showed their elevation credentials again this time round to inflict defeat on the Owls.
And in truth, the South Coast side were good value for the points, building on an encouraging start to weather a brief second half storm and seal victory.
Both goalscorers caused problems from the off – Knockaert dragged narrowly wide and Baldock saw a similar effort fall the wrong side of the upright.
The Owls grew into the game, though, and Barry Bannan thumped a vicious volley inches over the crossbar, only for Brighton to counter with a Jamie Murphy cross that almost crept in at the back post.
The contest levelled out until Brighton took the lead on 27 minutes. Lewis Dunk sent Baldock clear with a pinpoint pass and the striker cleverly lobbed Keiren Westwood, who got a hand to the chip but not enough to prevent the opening goal.
Wednesday rallied approaching the interval as Adam Reach and Fernando Forestieri went close, the latter a whisker away with a glancing header from Jack Hunt’s feed.
Westwood, who earlier suffered what seemed a thigh strain, came off at half time, giving Cameron Dawson his maiden first team appearance.
The early throes of the second period offered few talking points, although the Owls had a spell of pressure just after the hour that had Brighton rocking.
Tom Lees almost levelled on 69 minutes, thumping a fierce header goalwards but Oliver Norwood was perfectly placed to clear off the line.
And that proved pivotal as the visitors doubled their lead on 73 minutes.
Gaeten Bong found room in the penalty area to find the menacing figure of Knockaert, who smashed home from six yards.
Wednesday pressed in the closing stages - David Stockdale saved acrobatically from Ross Wallace, Steven Fletcher shot inches off target - and Hooper struck with almost the last kick of the game to halve the deficit.
Wednesday: Westwood (Dawson 46), Hunt, Loovens, Lees, Pudil (Hooper 48), Wallace, Bannan, Lee, Reach, Forestieri, Fletcher