Inter wasted the opportunity to increase pressure on Roma in the pursuit for the final Champions League spot in Serie A after a 1-0 defeat away to Genoa.
A close-range finish from defender Sebastian De Maio 13 minutes from time left Roberto Mancini's side frustrated after failing to convert a series of golden chances in the first half.
De Maio was on hand to slam the ball into the roof of the net after a well-directed header from substitute Panagiotis Tachtsidis for his first league goal of the season.
Inter were left rueing their profligacy in front of goal during a frenetic opening period. Ivan Perisic was twice denied by Genoa goalkeeper Eugenio Lamanna and top scorer Mauro Icardi had a header cleared off the line.
The defeat leaves Inter seven points behind Roma with four games remaining.
Inter had not won at the Stadio Luigi Ferraris since 2011 and, with Genoa unbeaten in seven home games heading into Wednesday's match, it was always going to be a tough ask. But on the back of their victory over title-chasing Napoli at the weekend, Inter will feel this was a wasted opportunity to build momentum.
Inter started brightly and almost went ahead within the opening five minutes, when Perisic's looping header was deflected towards goal and acrobatically clawed away by Lamanna just under his crossbar. Marcelo Brozovic fired just over from the rebound.
A flurry of chances came Inter's way on the half hour, but they could not take advantage of any. First, Icardi's low header was hacked off the line by Ezequiel Munoz, and then Perisic again drew a smart save from Lamanna when he stooped low at the far post to meet a Brozovic free-kick.
That stirred the home side into action and they almost took the lead themselves when Leonardo Pavoletti met a corner but Samir Handanovic was able to parry.
Genoa tightened up at the back in the second half, but Inter still carved out good opportunities to break the deadlock. Brozovic breached the offside trap after 65 minutes, but no Inter player could latch onto his low cross across the box.
Genoa edged their way back into the contest, first going close from a quick breakaway and then were rewarded when De Maio broke the deadlock, much to the delight home supporters.
Tachtsidis' cushioned headed following a cross from the right found De Maio and he applied an emphatic finish.
Inter almost salvaged a point right at the death when substitute Eder found half a yard in the area, but his left-footed effort was dragged just wide of the far post.