Antonio Candreva and Keita Balde were on target against their former club as Inter's eight-match winning run in Serie A ground to a halt in a 2-1 defeat at Sampdoria.
The Nerazzurri were aiming to go top, at least temporarily, and Alexis Sanchez saw an early penalty saved at the Luigi Ferraris.
Another VAR check led to Candreva opening the scoring from the spot and Keita – on loan at Sampdoria from Monaco – doubled the hosts' lead in an enthralling first half.
Stefan de Vrij finally headed wasteful Inter onto the scoreboard after 65 minutes, but Antonio Conte's side failed to find and a leveller and remain second, one point adrift of Milan.