Chelsea enjoyed a timely return to form to outplay Tottenham Hotspur in a 2-0 away victory in the Premier League as Frank Lampard outwitted his former mentor Jose Mourinho in their managerial battle on Sunday.
Willian struck both goals for Lampard's side in the first half as Chelsea consolidated fourth place while Tottenham's dismal afternoon went from bad to worse as forward Son Heung-min was shown a red card just past the hour mark.
It was a dispiriting day for Tottenham on and off the field with allegations of racist behaviour by one of their fans.
Chelsea coach Lampard, who won two of his Premier League titles in Mourinho's first reign at Stamford Bridge, conjured a game plan that saw his side dominate from start to finish, aided by a woeful home performance.
Willian punished slack defending to drive in the opener after 12 minutes as a labouring Tottenham quickly looked like blowing their chance of leapfrogging Chelsea into the fourth spot.
A rush of blood from Tottenham keeper Paulo Gazzaniga gifted Chelsea a penalty, awarded by VAR and converted by Willian, just before halftime to put Chelsea in command.
Tottenham's hopes of a revival were scuppered when Son needlessly kicked out at Antonio Rudiger and was shown a red card, with the decision again being made by VAR.
If that were not bad enough for the hosts, Rudiger indicated that he had suffered racial abuse from the crowd, prompting several announcements over the public address system. An object was thrown at Chelsea keeper Kepa Arrizabalaga.
"Toni came to me and said he was listening in the crowd monkey noises," Chelsea captain Cesar Azpilicueta said. "I reported it to the referee."
It took the shine off a great day for Chelsea who have tightened their grip on fourth place after seeing their lead shrink with four defeats in their last five league games.
They opened up a four-point lead over fifth-placed Sheffield United with Tottenham six points back in the seventh spot.
It was the first time in 14 matches at home against one of his previous clubs that Mourinho had suffered a defeat and a fired-up Lampard clearly enjoyed the moment, celebrating long after the final whistle in front of the visiting fans.
"My players showed they could fight and play against a top team because Tottenham are a good team," Lampard said.
"They are a major rival and it shows the players what they can do under pressure."
Before kickoff, Tottenham were the form side, having won four of the five league games since Mourinho replaced Mauricio Pochettino. After this display, though, and the loss to Manchester United, the Portuguese's honeymoon is over.
Lampard tweaked his formation to a back three and it paid handsome dividends as they snuffed out Tottenham's attack and dominated the midfield, with N'Golo Kante and Mateo Kovacic superb.
Willian earned the man of the match plaudits, though, with a virtuoso display. After 12 minutes, he played a short corner with Kovacic, cut inside a lumbering Serge Aurier and fired past Gazzaniga.
Just before halftime, Gazzaniga came racing out to claim Willian's dinked ball but only succeeded in clattering Marcos Alonso. Referee Anthony Taylor did not award the penalty, but a VAR check, correctly, gave it.
Mourinho sent on Christian Eriksen in the second half, taking off Eric Dier, but to little effect.
Chelsea had the ball in the net again but Tammy Abraham was offside and when Son saw red, it was game over for Spurs.
Sadly, the rest of the game was overshadowed by the allegations made by Rudiger.