Sampdoria moved up to fourth and piled more pressure on their former hero Roberto Mancini, who saw his Inter Milan side slump to a sixth straight defeat in all competitions and further out of the European race.
A stunning strike from Eder, the Brazilian-born player just called up by Italy, midway through the second half was enough to make it four wins on the bounce for coach Sinisa Mihajlovic - the former Inter player who both played alongside and under Mancini.
His side were deserving winners on the balance of play, and the performance will bring more questions for Mancini with the board demanding European qualification while nine points separate them from the top five.
It was an open start to the match with chances at both ends.
Mauro Icardi broke the Sampdoria offside trap but misplaced the following pass when trying to lay it inside, while moments later at the other end, Luis Muriel used some lovely skill to bring down a high ball, only to lash the following shot over the crossbar.
Icardi then headed over before Eder's low shot caused Samir Handanovic problems before he scrambled it away.
Eder then fired another shot over from an angle while Muriel almost scored a fabulous goal on the counter-attack in the 34th minute, running almost the entire length of the pitch, shaking off Andrea Ranocchia as he tugged his shirt, and then sending a dangerous shot narrowly over.
The half ended with Icardi going close again, but his shot was over the bar.
Inter began the second half very brightly, with Icardi's cross-shot striking the bar before Xherdan Shaqiri went close on the follow up.
Fredy Guarin's low shot was turned away for a corner, from which Lukas Podolski should have scored but instead struck air as he mistimed his shot.
Icardi once again headed over in the 56th minute and Inter would pay for failing to take their chances.
Danilo D'Ambrosio was booked for a foul on Roberto Soriano and Samp worked a neat short free-kick routine before Eder lashed an unstoppable shot in off the far post in the 65th minute.
Four minutes later, they almost repeated the trick but this time Eder's shot dipped too late and went over.
They threatened again in the 73rd minute as Samuel Eto'o and Eder combined to set up Pedro Obiang but he was denied by Ranocchia's last-ditch tackle.
Inter were struggling to find a response with the best they could manage a shot from Guarin which went high and wide in the 77th minute.
Guarin went closer in stoppage time when Emiliano Viviano misjudged his shot, but Sampdoria scrambled it away and took the win.
Udinese 2, Fiorentina 2
Two second-half goals from Mario Gomez were not enough for Fiorentina to take all three points at Udinese on Sunday evening.
Fiorentina came to life in the second half after Udinese defender Molla Wague had given the hosts a 15th-minute lead.
Germany forward Gomez headed in an equalizer five minutes into the second half before he put the Viola ahead three minutes later.
However, Panagiotis Kone pulled Udinese level in the 62nd minute and the Friuli took a share of the spoils.
It was a costly result for Fiorentina, as they lost ground on the battle for a top three place and a ticket to the Champions League.
They have fallen to sixth in Serie A, six points adrift of third-place Lazio, who won 2-0 against Hellas Verona.
Udinese, with just one victory in their last seven league games, remain in 12th place but they have a game in hand.
Napoli 1, Atalanta 1
Napoli lost ground in the race for a place in the Champions League as they were held to a 1-1 draw at home by struggling Atalanta, who ended the game with 10 men after Alejandro Gomez was dismissed.
Duvan Zapata saved Rafael Benitez's men from an even worse fate with his late equalizer after Mauricio Pinilla's goal for Atalanta while the hosts ended the game without the Spaniard on their bench after he was sent to the stands.
The draw means the Azzurri slip behind Sampdoria into fifth place in the standings, now five points behind third place and Champions League football next season - their minimum goal for the season.
Napoli may have booked their place in the quarter-finals of the Europa League, where they will play Wolfsburg next month, but qualifying for the Champions League next season remains their overall priority with three points at the Stadio San Paolo essential on Sunday night.
Cesena 0, Roma 1
Daniele De Rossi's first-half strike handed Roma all three points at relegation-threatened Cesena on Sunday night.
The visitors, looking for their first Serie A win since February 8, took the lead at the Dino Manuzzi stadium in the 41st minute when De Rossi hit the back of the net for his first goal away from home in Italy's top flight since August 2013.
The victory has kept Roma in second place but just one point clear of city rivals Lazio, who clinched their sixth straight victory with a 2-0 triumph over Hellas Verona.
Juventus are 14 points clear of Roma at the top of the standings.
Cesena, who had gone unbeaten in their previous three matches, are 19th and five points adrift of safety.
The Giallorossi have been struggling in 2015. They lost 2-0 to Sampdoria last week in Serie A - their first home defeat in Serie A since May 2014 - before falling 3-0 at home to Fiorentina on Thursday to crash out of the Europa League.
Roma coach Rudi Garcia, who has been under pressure with his team not playing well, fielded a weakened side with eight players out injured and midfield pair Seydou Keita and Miralem Pjanic out through suspension.
Parma 0, Torino 2
Torino inflicted more misery on Serie A strugglers Parma after they claimed a 2-0 win over the bankrupt club on Sunday.
Maxi Lopez and Migjen Basha scored for Torino while Parma were forced to play more than half of the match with 10 men after defender Alessandro Lucarelli was sent off in the 36th minute for a second bookable offense.
The result saw Torino move up to seventh place while Parma, whose future remains unclear, stayed rock bottom of the overall standings with just nine points.
The Ducale club, who were declared bankrupt by an Italian court on Thursday but are able to complete the season with the Italian football league providing the capital, have won just three league games this season. They lie 16 points adrift of safety.
The win put Torino seven points adrift of Napoli in fifth in the final Europa League place.
Lazio 2, Hellas Verona 0
Lazio reeled off their sixth consecutive Serie A win on Sunday when they claimed a 2-0 triumph over Hellas Verona.
Looking to keep the pressure on second-place Roma, Lazio took the lead when Felipe Anderson scored his ninth goal of the campaign in the fourth minute.
Not long after, Vangelis Moras nearly pulled the visitors level but he was denied by the post.
After Lazio's Lucas Biglia hit the crossbar in the 27th minute, the hosts doubled their lead on the stroke of half-time when Antonio Candreva hit the back of the net with a free-kick.
The Biancoceleste almost added to their advantage but Felipe Anderson hit the bar just past the hour mark.
The outcome at the Stadio Olimpico has kept Lazio in third place and just one point behind city rivals Roma, who won 1-0 at Cesena.
Hellas, unbeaten in their previous four games, did not produce the same performance that saw them defeat Napoli 2-0 last week.
They have dropped two places to 16th in the standings.
Lazio went into the contest having given away just one goal in their last five games.
