Image source, Getty Images
Sporting beat Benfica 1-0 in the league back in December
Gary Rose
BBC Sport journalist
The Lisbon derby is one of the most fiercely contested in the world but Sporting and Benfica meet on Saturday with even more than usual at stake.
That's because the two sides are top of Liga Portugal, level on 78 points with two games of the season remaining.
If the two teams are level on points by the end of the season then head-to-head record will decide the title winner, meaning Saturday could well be the day that decides who will be champions.
Everything to play for.
'Biggest derby in many years' what could happen on Saturday?
It has the potential to be a real winner-takes-all fixture.
Sporting, having won the first fixture earlier this season 1-0, will will be champions with a victory, as Benfica could then only finish level on points with them with a worse head-to-head record.
But Benfica have the advantage of being at home and if they win by at least a two-goal margin then they will reclaim the title.
Things could get even more interesting if Benfica win 1-0.
That would mean both sides have an identical head-to-head record and in that case goal difference would decide the title winner on the final weekend of the season. Currently, Sporting are three goals better off than Benfica.
"This is the biggest derby in many, many years," Filipe Ingles of Benfica FM told BBC Sport.
"I believe there's been five situations throughout history where Benfica and Sporting met in the penultimate game and both could be champions - Benfica won on four occasions, Sporting won the game and the title once."
CNN Portugal journalist Joao Paiva added: "This game will have extra spice in it as something that has never happened before might happen - Sporting could become champions in Benfica's home stadium.
"Just because of that they will not want to lose the game and see their rivals celebrate in their stadium."
The Lisbon derby: One of Europe's fiercest rivalries
Mid-season managerial changes spark revival
Image source, Getty Images
Ruben Amorim was in charge of Sporting for four years from 2020, winning the league twice
Sporting won the league for the 20th time last season and started the current campaign with 12 successive wins.
But the departure of Ruben Amorim to Manchester United in November disrupted them and his replacement - Joao Pereira - lasted just 42 days after a bad run of results.
"Manchester United did us a huge favour," added Ingles.
[After Amorim left] Sporting chose an inexperienced coach but it went so bad that after a few games they chose another coach called Rui Borges.
"Under Borges they don't play as well as with Amorim, but they became competitive again."
Benfica, too, made a managerial change after the season got under way, with Bruno Lage returning for a second spell in charge after Roger Schmidt was sacked just four games in.
That change also proved wise and they have kept up the pace with Sporting, winning 12 of their past 13 league games to have them within touching distance of a first league title since the 2022-23 season.
"In more than 70 years Sporting have never been champions two seasons in a row" added Paiva.
"Benfica want to become champions because they are the team in Portugal with the most titles. Sporting are way, way behind on that and want to start closing the gap."
'Like Man Utd and Liverpool meeting with winner taking title'
The Lisbon derby is one of the fiercest in Europe and before the game fans of the away team will march the couple of miles through the city to the opposition ground.
It is a rivalry that dates back more than a century, with the sides who would become officially known as Sporting Clube de Portugal and Sport Lisboa e Benfica first meeting in 1907 at a time when there was a huge class divide between them.
Sporting, bankrolled by the Viscount of Alvalade, had already riled their rivals by taking eight of their players on the promise of better facilities and won 2-1.
Benfica's image as the people's club was, meanwhile, encapsulated in 1954 by their fans helping to build the original Estadio da Luz, a stadium that boasted its record attendance of 135,000 for a game against Porto in 1987 and was their home until the new ground was built before Euro 2004.
Then there was the legendary Eusebio, who played for Sporting's feeder club Sporting Clube de Lourenço Marques in Mozambique but ended up signing for Benfica and helping them to 11 league titles and a European Cup in 15 seasons, while also winning the Ballon d'Or.
This will be their third meeting this season, with Benfica beating Sporting on penalties in the League Cup final in January, and they will meet again at the Jamor National Stadium in the Portuguese Cup final on 25 May.
"Of course, the entire country is very excited for this," Ingles said.
"Around 90% of Portuguese people support Benfica, Porto or Sporting, so this is not only a Lisbon derby, but a national derby.
"Two thirds of our population support Benfica and Sporting so the country will literally stop to see this.
"Imagine Manchester and Liverpool, or Arsenal and Tottenham meeting at game 37 and whoever wins the game, wins the league,
"It's massive and the atmosphere in the stadium and in the country will be electrifying."