Ole Gunnar Solskjaer's Besiktas beat Fenerbahce 1-0 in the Istanbul derby to further dent Jose Mourinho's chances of winning the Turkish Süper Lig.
Gedson Fernandes, who flopped at Tottenham Hotspur when Mourinho was in charge, missed a penalty but then scored the only goal to hand Solskjaer bragging rights at Sukru Saracoglu Stadium.
The win sees Solskjaer became the first foreign Besiktas coach to claim an away win at Fenerbahce in 22 years and spells the end of Fenerbahce's title hopes, with Mourinho's side eight points behind leaders Galatasaray.
The former Manchester United managers, who together spent five years at Old Trafford, clashed during their time in England and faced each other for the first time since moving to Turkey.
Solskjaer replaced Mourinho at United in 2018 and the two managers both recorded second place Premier League finishes - the highest the Red Devils have achieved since Sir Alex Ferguson.
The pair locked horns in April 2021 after Solskjaer's United beat Spurs 3-1, a week before Mourinho was sacked.
The 62-year-old Portuguese boss was incensed after Solskjaer claimed Son Heung-min had cheated to disallow a United goal.
Solskjaer, who revealed pre-match he has not spoken to Mourinho since his arrival in Turkey in January, criticised the South Korean for diving at the time.
'If that was my son and he stays down and he needs his mates to help him up, he doesn't get food because that's embarrassing, the game's absolutely gone,' the Norwegian said.
Mourinho took aim at Solskjaer's parenting in response.
'I just want to say that Sonny is very lucky that his father is a better person than Ole,' he said.
'I am a father. I think as a father you have to always feed your kids. It doesn't matter what they do. If you have to steal to feed your kids, you steal.
Solskjaer shrugged off the rivalry before the game, insisting: 'This is not a match between Jose Mourinho and Ole Gunnar Solskjaer.
'This is a match between Besiktas and Fenerbahce. The players will decide the score. I have great respect for Mourinho.'
Since replacing Giovanni van Bronckhorst in January, the 52-year-old has lifted Besiktas to fourth place in the league and are competing for Europa League play-off spot.
Fenerbahce will compete in the Champions League next season but there is uncertainty whether Mourinho will still be in charge.
In November he tore into the Turkish Super Lig in an incredible tirade following his team's 3-2 away win at Trabzonspor on Sunday.
Mourinho did not hold back as he boldly stated: 'Nobody abroad wants to watch the Turkish league.
'Who wants to watch this Turkish league abroad? They have the Premier League, they have the French league, they have the German league, they have the Portuguese league, they have the Dutch league. Why should they see this?
'It's too grey. It's too dark, smells bad. But that's my job, and I will give everything to my job, to my club.'
Meanwhile, the former Chelsea manager was last month hit with a three-match ban and slapped with a 292,500 Turkish Lira (£5,955) fine after appearing to grab the nose of Galatasaray boss Okan Buruk in jaw-dropping scenes.
After approaching Buruk from behind, Mourinho seemingly pinched his opposite number's nose. Buruk, 51, then fell to the floor, covering his face with his hands.