Slaven Bilic believes West Ham's dramatic 2-1 victory over Liverpool tonight will be remembered as one of the "greatest games" in the club's history.
Michail Antonio's volley put the hosts in front on the stroke of half-time but the Hammers' hard work was undone immediately after the break.
Philippe Coutinho drilled a cheeky free-kick under the wall and into the bottom corner to pull the visitors level.
Both sides had chances to win the game as Christian Benteke and Daniel Sturridge went close but the teams could not be separated until deep into extra time.
The tie appeared to be destined for penalties but Angelo Ogbonna popped up to head home a last-minute winner.
Dimitri Payet swung a free-kick into the penalty area and the Italian defender rose highest to power his effort past Simon Mignolet, much to the delight of the Upton Park faithful.
Bilic was delighted to see his side book their place in the fifth round and is adamant the encounter will be remembered for years to come: "It's going into the history of West Ham's greatest games," he told BT Sport.
"No matter it is only for the last 16 but this is against Liverpool, a late night kick-off, in the last season at Upton Park, a great game and a goal in the last minute.
"I think we deserved it. I'm very proud of the guys. They left their heart on the pitch. I'm simply very, very proud of the boys tonight."
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The Croatian manager also singled out Ogbonna, who stifled the threat of Benteke for the majority of the game, for individual praise.
"I told Angelo regardless of the goal - the goal came as the cherry on the pie of his game.
"His game today was magnificent. He deserved the goal in the dying seconds of the game."
West Ham's busy fixture list will become even more congested now they have booked their place in the last-16 but Bilic believes special nights make all of his team's effort worthwhile.
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"Unfortunately it wasn't the final! We're going step by step. We're going to be tired and we won't have a break after the Norwich game because we will play Blackburn.
"But it's all worth if because of nights like that," added the Croatian.
