Salernitana stunned Lazio with a stormy 3-1 Serie A win on Sunday, ending their hosts' hot run of form a week from the season's first Rome derby.
Without injured star striker Ciro Immobile, Lazio looked set to claim their sixth win in seven league matches and provisional second place when Mattia Zaccagni rolled them ahead four minutes before half-time in Rome.
Lazio had not conceded in their previous six Serie fixtures but Salernitana didn't lose their heads and came away with their first ever win at the Stadio Olimpico, leaving Lazio fourth and eight points behind league leaders Napoli.
"I had some great years here at the Olimpico. I feel at home when I come back here, I'm very happy," said scorer Federico Fazio who left Roma in January after over five years in the capital.
"It's good to come back here, I played a lot of games here and I have a lot of memories."
Ex-Lazio man Antonio Candreva brilliantly lobbed Salernitana level in the 51st minute and soon after Maurizio Sarri's team were stung by another old boy, this time Fazio of their hated local rivals.
Federico Fazio collected from Flavius Daniliuc's miscontrol and smashed the away side ahead in the 68th minute, shocking the home crowd and sparking a furious attempt to get back on level terms.
In their haste star man Sergej Milinkovic-Savic -- who had started from the bench as he was one booking away from being suspended -- was given a soft yellow card after running into Dylan Bronn.
The Serbia midfielder will now miss next week's derby with Roma, who can move a point above Lazio and Inter Milan with a win at Verona on Monday.
And while fans loudly voiced their disapproval, Boulaye Dia slid in Salernitana's third at the end of a lightning counter-attack to earn his team a creditable ninth place after only just staying up last season.
LOOKMAN ON FORM
Atalanta are second after Ademola Lookman netted his fourth goal in five league matches in a 2-0 win at Empoli which continued his fine run of form.
The Nigeria international ensured Atalanta moved above champions AC Milan, who are at Torino in Sunday's late match, with a low finish just before the hour mark.
Gian Piero Gasperini's side are five points behind Napoli.
"He has technique, pace, is a player any coach would be happy with," Gasperini said of Lookman to DAZN.
"We realised pretty quickly what he was capable of, he was convincing from the start."
Hans Hateboer jabbed home the away side's opener in the 32nd minute after Lookman's shot was deflected into the Dutch international's path just inches from an open goal.
Atalanta would have run out even more convincing winners had Teun Koopmeiners' penalty not been saved by Guglielmo Vicario just before the break, after Mattia Destro handled Lookman's free-kick.
Empoli sit 13th after their fifth defeat of the season, two points behind Fiorentina who won 2-1 at Spezia thanks to Arthur Cabral's last-minute winner.
Udinese were on Napoli's heels earlier in the month but are now 10 points off the pace in eighth following their third draw in their last four matches, 0-0 at bottom team Cremonese.
Andrea Sottil's team are two points off the Champions League places but would be in the top four had Gerard Deulofeu not wasted a great chance in stoppage-time.