London: All eyes will be on Chelsea manager Jose Mourinho and Tottenham boss Andre Villas-Boas as the former friends meet in a bitter grudge match on Saturday.
Any derby between Spurs and Chelsea offers the potential for an explosive encounter, but Mourinho's dysfunctional relationship with his former pupil Villas-Boas makes the London rivals' latest clash at White Hart Lane even more flammable than usual.
Mourinho was infuriated this week when Villas-Boas lifted the lid on the simmering tensions between the two Portuguese coaches, who have gone from close colleagues to feuding enemies in the space of four years.
"We had a great personal and professional relationship before that we don't have now," Villas-Boas said.
"I don't think we need explanations. But our relationship broke down.
"I think we have the mutual respect for each other and we understand what we have been through cannot just disappear but it's not like it was before."
Mourinho responded by attempting to take the moral high ground, saying: "I don't describe (the relationship), because I'm not a kid to discuss relationships with the media. It's a personal thing.
"I don't care what he says. I'm here, not to comment on what he says or what to know what he says. I'm not interested."
The enmity between the two grew slowly over the years.
Villas-Boas, who worked as a scout compiling dossiers on opponents, was a trusted member of Mourinho's backroom staff at Porto, Chelsea and Inter Milan.
Crushing loss to City

Crushing loss to City
But the first fracture in their relationship occurred when Mourinho rejected Villas-Boas's request for more involvement in coaching, a decision that prompted Villas-Boas to quit Inter to go it alone as a manager in Portugal.
When Villas-Boas eventually took over at Porto and credited legendary boss Bobby Robson, rather than Mourinho, with his rise to prominence, the rift grew wider still.
Now they will face off for the first time since their separation in 2009 and there have been enough barbs between the pair over the last few months to suggest the bench at White Hart Lane will be as closely watched as the action on the pitch.
Meanwhile, leaders Arsenal, unbeaten in eight games in all competitions, visit a Swansea City side smarting after their League Cup defence was ended by second-tier Birmingham City.
Manchester United reacted to their 4-1 derby humiliation at Manchester City last weekend by eliminating Liverpool in the League Cup and the champions will hope to get back to winning ways in the league by defeating West Brom.
The crushing loss to City left the champions five points below Arsenal in eighth place, but centre-back Jonny Evans says he has known darker days at Old Trafford.
"I have been on the training ground where the atmosphere has been worse than it was when we came in the day after the (City) game," Evans said.
"We had no complaints at the weekend. Everyone was honest in their assessment that we didn't apply ourselves the way we should have.
"It is hard for the fans, the players and the manager as well. We just had to move on from it quickly."
City continued their goal-scoring form by avenging last season's FA Cup final loss to Wigan Athletic with a 5-0 League Cup win over the Championship side in mid-week, ahead of a trip to Aston Villa on Saturday.
Montenegro striker Stevan Jovetic opened his account for City with a brace and will hope to keep his place in the starting line-up at Villa Park.
The post-Paolo Di Canio era continues for Sunderland with a home game against Liverpool on Sunday, when caretaker coach Kevin Ball will once again be in charge of first-team affairs.
Liverpool can call upon last season's top scorer Luis Suarez for the first time in the league this season, after he returned to action in the mid-week loss to United following a 10-game ban for biting Chelsea's Branislav Ivanovic.