London - Facing a crunch match against Liverpool on Saturday, embattled Chelsea manager Jose Mourinho must confront an adversary who condemned him to one of the most painful defeats of his career.
Jurgen Klopp, Liverpool's new manager, was in charge of the Borussia Dortmund side who ousted Real Madrid in the 2012-13 Champions League semi-finals, dashing Mourinho's dream of bringing the European Cup back to the Bernabeu in what he knew would be his final season at the club.
The pair resume hostilities with Mourinho reported to be facing the sack if results do not improve after the defending champions slumped to 15th place in the Premier League and were knocked out of the League Cup by Stoke City, but he has drawn hope from their recent upturn in performances.
Asked how hard it would be to lift his players after they relinquished their League Cup crown at Stoke, Mourinho said: "It's difficult. But it's more difficult when you play very badly and lose, than playing well and losing.
"How can (Eden) Hazard or Oscar or (John) Mikel (Obi) or John Terry, to say some names - I could say everyone - how can they go home with a lack of confidence? They played well. They didn't make many mistakes."
Mourinho is expected to be in the dug-out despite having been hit with a Football Association misconduct charge after being sent to the stands during last weekend's 2-1 loss at West Ham United.
But the bad news continues to pile up for the 52-year-old.
Young Brazilian forward Lucas Piazon, on loan at Reading, is the subject of an arrest warrant over an alleged sexual assault in Canada, while former team doctor Eva Carneiro is believed to have begun legal proceedings against the club after being sidelined by Mourinho earlier in the season.
Reports differ as to the likely consequences of another defeat for Mourinho, but there is general consensus that his future at Stamford Bridge is on the line.
The dismissal of Klopp's predecessor Brendan Rodgers was a stark reminder of the cost of failure in the English top flight and while the German drew his first three games, his side will travel to London on the back of a 1-0 League Cup win over Bournemouth.
With his back to the wall, Mourinho needs his senior players to stand up and be counted, but he may be without Diego Costa after the striker went off against Stoke with a badly bruised rib.
Should Costa not be passed fit, Loic Remy is in line to deputise and although Chelsea are nine points adrift of the top four, the French striker remains confident of Champions League qualification.
"Saturday will be a big game, but we can still be in the top four of the league if we win games," Remy said.
"When you know the quality of the group and the fact we were were champions last season, which was not by chance, the quality is still here."
Klopp has also been inconvenienced by injury, with Kolo Toure, forced off against Bournemouth, the latest casualty, while Daniel Sturridge is taking time to recover from a knock sustained in training.
But James Milner is back from suspension and Klopp is hopeful that Christian Benteke will be able to lead the line after missing the Bournemouth game with a knee ligament strain.
"I think Christian will be fit on Saturday," Klopp said. "He had little problems and with our striker situation, we can't take a risk."
Liverpool have not beaten Chelsea in eight matches and have not won at Stamford Bridge since November 2011, when they won twice there in the space of 10 days in the league and League Cup.
But Klopp got the better of Mourinho when their paths crossed in 2012-13, with Dortmund taking four points from Madrid in the group phase of the Champions League before eliminating them in the last four.
A similar outcome on Saturday could have grave repercussions.