Fighters react to Jairzinho Rozenstruik's last-gasp KO win vs. Alistair Overeem

Jairzinho Rozenstruik remained undefeated in the UFC, stopping Alistair Overeem with just four seconds left in their fight on Saturday night. Jeff Bottari/Zuffa LLC via Getty Images

The UFC Fight Night main event Saturday featured veteran star Alistair Overeem taking on a young powerhouse in Jairzinho Rozenstruik. And through most of the fight, it was the former Strikeforce heavyweight champion Overeem getting the better of the inexperienced but undefeated Rozenstruik, who entered the fight at 9-0.

In fact, all three judges had Overeem ahead on their scorecards entering the fifth round. With the clapper sounding, signifying the final 10 seconds of the last round, it was all but academic in Washington D.C. "The Demolition Man" was set to chalk up another victory.

But Rozenstruik wasn't done. He clipped Overeem with a left, then dropped him with a right, opening a nasty gash on his lip in the process. Overeem immediately got back up, but referee Dan Miragliotta stopped the fight with just four seconds left.

Needless to say, Rozenstruik's late KO and images of Overeem's bloody lip had the MMA world buzzing on social media, including prompting UFC president Dana White to tweet "Holy s---" and Francis Ngannou responding to Rozenstruik's postfight call out.