Although Isaac Price’s first international goal quickly cancelled out Andraz Sporar’s third-minute strike, Petar Stojanovic’s strike deflected off Jonny Evans to put the hosts back in front in a frantic start to the match, and Benjamin Sesko added a third before the break.
Evans got Northern Ireland back into it with a deflected strike in the 53rd minute, but only briefly as Sporar got his second moments later.
Defeat leaves Northern Ireland three places and seven points off second in Group H going into Sunday’s trip to Kazakhstan, with the dream of heading to Germany next summer effectively dead.
After three straight 1-0 losses Michael O’Neill could again claim his side had not been hugely outplayed, with Conor McMenamin particularly impressing as they created more chances than Slovenia.
But Northern Ireland’s defensive solidity deserted them and they simply do not have the firepower to match the likes of RB Leipzig’s Sesko.
The 20-year-old was involved as Slovenia breached the Northern Ireland defence inside three minutes. Shea Charles missed an interception and Sesko easily flicked the ball into the path of Sporar, who had time to beat the exposed Bailey Peacock-Farrell.
It was a dreadful start, but somehow Northern Ireland roused themselves to equalise with their first goal since the opening qualifier against San Marino in March.
McMenamin and Matty Kennedy – earning his first cap since March 2021 – came into the side as O’Neill stuck to his word to choose players in form at club level, with all but Evans having been regulars in the opening weeks of the season, and both were involved in the equaliser.
McMenamin’s cross from the right was aimed at Kennedy and when his shot was blocked by Atletico Madrid’s Jan Oblak, it fell for Price to fire in.
But soon after Slovenia were back in front. Stojanovic left Ciaron Brown in a heap as he cut in from the right, with the Sampdoria man’s cross taking a deflection off the luckless Evans to beat Peacock-Farrell as Northern Ireland appealed in vain for a foul.
It was the last involvement for Brown, who became the 17th Northern Ireland player to suffer an injury in this campaign, hobbling off to be replaced by Craig Cathcart – playing his first competitive football since June a day after signing for Belgian club Kortrijk.
McMenamin’s cross narrowly evaded Paddy McNair but it was Slovenia who thought they had a third 10 minutes before half-time when Sesko finished from close range, with the loud celebrations cut short once the stadium DJ belatedly noticed the flag was up for offside and play had resumed.
But Sesko would have his goal before the break. After Kennedy missed a chance to clear, Sesko wriggled away from Evans with his back to goal before hitting a powerful low left-footed strike on the turn to find the corner of the net.
O’Neill sent on Josh Magennis and Conor Washington for Kennedy and Dion Charles at the break but it was Slovenia who threatened again, with Sporar seeing a powerful effort cannon back off the crossbar from close range.
Hope was rekindled in the 53rd minute when a deflected strike from Evans beat the scrambling Oblak.
But that hope lasted barely three minutes before Sporar raced through the centre of the pitch, rounding Peacock-Farrell and rolling the ball into an empty net, and Northern Ireland could not capitalise on late chances for Magennis, McMenamin, and substitute Paul Smyth.
Northern Ireland’s injury curse struck again 15 minutes from time as the substitute Cathcart hobbled off, as if to underline the problem that has dogged Northern Ireland since before this doomed campaign began.