Watch: Dustin Jacoby delivers a clean one-punch walk-off knockout of Jung Da Un at UFC Long Island

UFC Long Island is in full swing, and during the prelims, we have already been presented with our first devastating knockout. Dustin Jacoby delivered a sickening one-punch knockout against Jung Da Un.

The New York card is filled with brilliant matchups and a handful of potential Fight of the Year contenders, but none more so than the main event of the evening. In a five-round headliner, Brian Ortega and Yair Rodriguez will lock horns, attempting to earn a shot at Alexander Volkanovski for the featherweight title next.

In a stand-and-bang type of fight, Dustin Jacoby came out on top after earning a beautiful finish a little over three minutes into the first round, leaving Jung Da Un in a daze.

Watch the finish below:

Despite the nature of the finish, it wasn't a one-sided fight. Credit must go to Jacoby's Korean opponent for keeping the clash competitive for as long as it lasted.

The light heavyweight division now has another surging prospect, and the former GLORY kickboxer will expect to fight somebody higher than his No.15 ranking in his next outing.

For Jung Da Un, although the outcome wasn't one he would have envisioned, this loss serves as his first since signing with the UFC. It shouldn't be long before we see the 28-year-old back to winning ways.

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Dustin Jacoby's time in the UFC

The former boxer and kickboxer made his transition to MMA in 2010. Despite having an impressive start to his time in the sport, that changed when he entered the octagon.

Making his UFC debut back in 2011 with a perfect 6-0 record, Dustin Jacoby suffered back-to-back losses and was unfortunately cut from the promotion without gaining a single win.

Following his release, five wins in his next eight and a Cage Fury FC middleweight championship earned him a chance in Dana White's Contender Series. The 34-year-old hasn't looked back since.

A decision win over Ty Flores moved the contender to a 12-5 record and subsequently earned him a UFC contract. The finishes of Justin Ledet, Darren Stewart, and the aforementioned Jung Da Un are the light-heavyweight's standout fights in the promotion.

Alongside his knockout wins, Dustin Jacoby has earned three separate unanimous decisions over Maxim Grishin, John Allan, and the dangerous Michal Oleksiejczuk. A draw against Ion Cutelaba rounds out his career with the UFC so far. His record in the promotion currently stands at six wins, two losses, and one draw.