Sampdoria completed their first double derby triumph over city rivals Genoa in 57 years on Saturday thanks to a 1-0 win.
Luis Muriel scored the only goal of the game on 71 minutes after breaking away from a poor tackle from Ezequiel Munoz to drive the ball past Eugenio Lamanna in the Genoa goal.
The Colombian striker was booked for his extravagant celebrations but that didn't dampen Sampdoria fans' joy after their side had defeated Genoa twice in the same seasons for the first time since 1960.
Sampdoria are up to ninth place in Serie A while Genoa are down in 15th but 14 points above the relegation zone.
Juventus went 11 points clear on Friday when a contentious injury time penalty gave them a 2-1 win over 10-man AC Milan and a 31st successive home triumph.
The defending champions looked set to be held by their old rivals, who had stunned the 32-time Serie A winners 1-0 at the San Siro earlier in the season, after Carlos Bacca had cancelled out Medhi Benatia's opener for the league leaders.
But in the closing minutes, Milan lost Jose Sousa to a red card for lashing out at Kwadwo Asamoah before Mattia De Sciglio was penalised for hand ball.
Argentine striker Paulo Dybala kept his nerve to slot the penalty past teenage goalkeeper Gianluigi Donnarumma who had pulled off a series of stunning saves to keep Milan in the game.
The three points also allowed Juventus to look ahead to their Champions League last 16 return against Porto, who they lead 2-0, next week.
Juventus coach Massimiliano Allegri admitted he hadn't seen the penalty converted.
"The game was over. I was already in the tunnel and I preferred not to see the penalty," Allegri said.
"We were going to either win or draw. Paulo did well, because it’s never easy to put a penalty past Donnarumma, especially in the form he was in tonight."
Milan coach Vincenzo Montella attempted to play down the controversy over the penalty which had led to angry scenes with his players venting their frustration with the referee.
"I don’t want to talk about referees but there is a big difference between a penalty 10 minutes in and one at the 95th minute," Montella told Mediaset Premium.
Juventus suffered a setback in the warm-up when Croatian striker Mario Mandzukic was struck down with illness.
But the champions were soon into their stride and deservedly took the lead on the half-hour mark when Moroccan centre-back Benatia was picked out by a Dani Alves cross over the top of the defence.
Benatia chested down the pass and drove the ball beyond the despairing dive of 18-year-old 'keeper Donnarumma.
But Juve were put on the back foot just before the break when Spanish winger Gerard Deulofeu danced down the flanks to set up Colombian international Bacca for the equaliser.
It was Bacca's fourth goal in his last three Serie A games.
Donnarumma then kept Milan in touch with saves from Miralem Pjanic, Sami Khedira and Gonzalo Higuain but he was left shattered by the last-minute drama.
Milan stay in seventh place, 20 points behind Juventus and seven off the final Champions League qualifying place.