Crotone extended Inter's winless run in Serie A to eight matches as Andrea Barberis' second-half equaliser secured Walter Zenga's side a well-deserved 1-1 draw at San Siro.
Playing in place of the injured Mauro Icardi, Eder marked his first league start of the season by heading the the Nerazzurri ahead in the 23rd minute, albeit visiting defender Davide Faraoni got the final touch.
Yet the out-of-sorts hosts laboured throughout and Crotone deservedly picked up a valuable point in their battle to beat the drop, Barberis reacting quickly to poke a loose ball beyond Samir Handanovic.
The result will be particularly pleasing for Zenga, a legendary name at Inter who is back coaching in his homeland after an unsuccessful spell at English Championship side Wolves.
As for his old employers, a fifth successive draw at least keeps Inter in fourth place in the table, though Roma can close to within a solitary point with victory away at Verona on Sunday.
8 - Inter Milan have equalled their longest winless streak in their Serie A history (eight games), recorded on five occasions - the latest in May 2017. Fasting. #InterCrotone
-- OptaPaolo (@OptaPaolo) February 3, 2018
After Inter won 2-0 in the previous meeting of the teams last September, they were riding high in the table having picked up maximum points from their first four outings in the campaign.
However, a miserable run of form either side of the mid-season break has emphatically ended talk of an unlikely title challenge and instead left Luciano Spalletti's side looking nervously over their shoulder in the battle to secure a top-four finish.
There was a collective sigh of relief around the San Siro when Eder opened the scoring, the forward heading Marcelo Brozovic's corner home via a deflection off defender Faraoni's shoulder.
Inter had to rely on a set-piece opportunity to break the deadlock though, as they struggled in open play during a tepid first-half display that demonstrated a lack of confidence running through the team.
Faraoni made amends for his accidental involvement in the opening goal with a crucial clearance to prevent a second after the break, cutting out Antonio Candeva's low cross as two Inter players waited to apply the finish in the middle.
The interception kept Crotone within touching distance, and the visitors grew in confidence with each minute that ticked by.
Their willingness to push more men forward paid off with an equaliser on the hour mark, Marcello Trotta's attempted return pass rebounding off the knee of Borja Valero to set up Barberis.
Spalletti's responded to conceding by summoning Rafinha from the bench, and the Brazilian came close to marking his home debut with a winner when his goal-bound shot was kept out by a diving Alex Cordaz.
Ivan Perisic summed up another disappointing outing by blazing over when well-placed to convert Danilo D'Ambrosio's cut-back pass from the right, while Inter were relieved to see Trotta's left-footed drive on the angle drift narrowly wide as an eventful finish saw both teams go close to grabbing a dramatic winner.