Twenty four hours after fourth tier Bradford City dumped out Aston Villa, Welsh side Swansea reached their first major English final with a 2-0 aggregate win after the second instalment of their semi-final ended in a dogged 0-0 stalemate.
As Swansea players and fans celebrated, the post-match focus swiftly turned to Hazard who was kicked out after 81 minutes.
A ballboy who was stubbornly refusing to return the ball and lying on top of it for good measure caused the Belgian to lose his cool as he tried to kick the ball from underneath the youngster but in the process caught him in the ribs.
Referee Chris Foy called Hazard across and gave him his marching orders, ending any lingering hopes the visitors had of securing a route back into the tie.
Swansea's hard work had effectively been done at Stamford Bridge two weeks ago, but they were resilient in their rearguard determination and deservedly set up a final meeting with Bradford on February 24.
A final pitching one of the Premier League's less fancied clubs and a side plying their trade in the bottom tier of the football league was unsurprisingly not the main talking point on an evening that witnessed such a farcical finish.
"Demba Ba told me the ball boy held on to it but I saw him kick him and you can't do that to a young boy," Swansea captain Ashley Williams told Sky Sports.
Chelsea manager Rafa Benitez said his player had apologised following the match to the ballboy who walked away from the incident grimacing and clutching his side.
"Eden Hazard has been in to see the ballboy and the two have apologised to each other," Chelsea's interim manager said after a reverse that is likely to bring further scrutiny on his own position.
"The ballboy knows he was wasting time. We are disappointed to lose the player but we cannot change things."
Swansea will face Bradford in the final at Wembley Stadium after the minnows upset Premier League Aston Villa on Tuesday.
"Most of these players have never been to a final," Swansea manager Michael Laudrup said.
"I've been there a lot of times as a player and a manager and it is so different. It is absolutely amazing and you will always remember it. Even the ones I lost have been great."
Chelsea made one change from the team that beat Arsenal 2-1 in the Premier League on Sunday, with January signing Demba Ba taking the place of the out-of-sorts Fernando Torres.
The game was six minutes old when the Senegal striker was involved in controversy as he burst into the box and appeared to be tripped by Swansea defender Ben Davies, but Chelsea's penalty appeals were waved away by Foy.
Chelsea were spraying the ball around confidently, but the best early chance fell to the hosts.
Winger Wayne Routledge played a clever throughball for Michu, but the Spanish striker, whose superb start to life in the Premier League was rewarded with a new four-year contract on Wednesday, failed to find the co
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