Adam Kownacki is determined to bounce back following his first career defeat.

It wasn’t the night he was accustomed to at the Barclays Center in Brooklyn, but Adam Kownacki knew this was just part of boxing. One punch can change the dynamic of a fight, and “Babyface” was caught with a well placed one from Robert Helenius.

“It’s boxing, you gotta be careful at all times,” said Kownacki, who grew up in Brooklyn and made his tenth appearance at the Barclays Center. “One move of not being cautious, you get caught with a good shot; and the fight changes. Especially in the heavyweight division. But it was a learning lesson. I’m still young, I’m still beautiful. So I’ll be back.”

Kownacki (20-1,15KOs) appeared to have Helenius (30-3,19KOs) in trouble against the ropes to start the fourth round. But the determined underdog countered with a solid right hand, followed by a one-two combination. Helenius seemed to score a clean knockdown, with Kownacki’s right knee hitting the canvas. However, referee David Fields ruled it as a slip.

“The Nordic Nightmare” erased all doubt immediately by dropping Kownacki on his back with a hard left hook. The impact sent the pro-Kownacki crowd into a frenzy of shock and panic throughout the arena. Helenius then pressed forward and unloaded relentlessly, to which the Lomza, Poland native retreated and left the attack unanswered.

Fields had seen enough, and called a stop to the contest at 1:08 of the fourth round; giving Helenius the TKO victory in a big upset. Although Kownacki’s quest for a heavyweight title shot was brought to an abrupt halt, he looks upon other greats in the division’s history who have risen after falling.

“I wanna be the best,” said Kownacki. “I’ve got to prove I’m the best fighter. But via great fighters like Lennox Lewis, Lewis came back. A lot of great fighters lost and came back, so I’m about to do the same.”