Benfica welcomed Sporting to the Estadio da Luz, trailing their Lisbon rivals by four points, with the added twist that former manager Jorge Jesus would be returning in the visitors' dugout.
Jesus is the Encarnados' most successful manager in history, having guided the club to three domestic titles and two Europa League finals in his six-year spell at the helm, but a bitter contract dispute saw him leave for the green and white half of Lisbon over the summer.
The ill feeling still lingers. According to reports, Benfica have initiated legal proceedings against Jesus, alleging that he worked with Sporting while under contract and are looking for £14million in compensation - that's £1 for every supposed Benfica fan.
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Benfica's loss has been Sporting's gain as the Leoes went into the game joint top of the league, level with FC Porto. It's a welcome sight for Sportinguistas, who haven't seen their team win the domestic league title since 2002.
And it wasn't the only side note. The run up to the game saw outspoken Sporting President Bruno de Carvalho suggest that Benfica were annually spending over £100,000 on gifts and dinner for referees, and there was uncertainty whether De Carvalho would sit in the Presidential suite. He opted for the relative safety of the dugout.
Finally, after all the hype came the game itself.
It started at a frenetic pace as the home side tried to impose their quick passing style, with wingers Nico Gaitan and Goncalo Guedes seeing plenty of the ball.
But for all of Benfica's enthusiasm, they seemed to quickly run out of ideas when they were met with resolute defending from Sporting's Paulo Oliveira and Naldo.
The Leoes grew in confidence and Teo Gutierrez forced the ball past former QPR keeper Julio Cesar to put the visitors ahead on nine minutes.
That was quickly followed by some neat work down the left by Jefferson before his out swinging cross was met by Islam Slimani's firm header for 2-0.
The home side were flummoxed. Despite plenty of industry, Benfica were unable to create any telling chances. Frustration mounted both on and off the pitch and Jesus' calm persona on the touchline served to highlight the opposition's calculated approach.
And then, at 36 minutes, Bryan Ruiz slotted home to put Sporting three up at half time. It was reminiscent of Benfica at their best under Jesus.
New Benfica manager Rui Vitoria, who had said he felt his team would face 11 individuals instead of a team in the build up, found it was his side that lacked cohesion. A scrappy second half saw cards galore but by then the damage was done and Sporting ran out convincing 3-0 winners.
It was the first time Sporting had ever scored three first half goals at Benfica and it was also their biggest away win over their arch rivals in 67 years.
But much more than three points gained, it's the symbolism of the performance that may cause the most damage.
Sporting may not have just taken Benfica's manager, they may have taken their soul.
Do you think it was wrong of Jesus to move from Benfica to Sporting? Give YOUR opinion in the comment box below!