Underdog Robert Helenius has stunned Adam Kownacki to close in on a potential heavyweight world title fight.

The 36-year-old Finnish fighter stopped his opponent in the fourth round after a surprising display at the Barclays Center in New York.

Helenius came into the bout as a huge underdog, with his opponent Kownacki seen as a 20-1 favourite in some books for the WBA heavyweight title eliminator.

Kownacki was undefeated coming into the fight and was expected to add another victory to his impressive 20-0 (15KO’s) record.

But this didn’t intimidate Helenius, as he put Kownacki on the back foot early on by landing some huge blows. The Fin could now be in line for a world title shot against current WBA, IBF, WBO and IBO heavyweight champion Anthony Joshua.

Kownacki started the fight in usual style, coming forwards at Helenius to try and smother him with big shots. The fight soon turned out to be more even, however, with Helenius managing to land some significant blows in the second round that rocked the Polish-American fighter.

The fighters exchanged some big shots early on in the fourth round before Kownacki slipped. This seemed to spur his opponent on, as Helenius followed up with a clever combination to put Kownacki to the canvas.

Helenius continued to use his superior height and reach to his advantage, hitting Kownacki lots with no reply. The favourite was on unsteady legs and the referee quickly had to stop the bout.

Kownacki was once in line for a world title shot due to his impressive undefeated record.

He has beaten some strong fighters in his career, including Charles Martin, Gerald Washington and Artur Szpilka.

But it seems his opponent will instead be in line for a title shot, as Helenius could now challenge AJ if he overcomes his IBF mandatory challenger Kubrat Pulev first.

This result shows that you can never write off an underdog such as Robert Helenius, especially in the heavyweight division where all it takes is one big shot. Helenius will hope that this huge win can restart his career which is already in its later years.