After a sluggish first-round showing, Saint Preux tried for a takedown a minute into the second round, eventually getting Boser to the ground after they clinched at the fence. Boser was warned for grabbing the fence with his right hand as he worked his way to his feet, prompting Saint Preux's corner to scream foul.
Replays were unclear whether he had indeed grabbed the fence.
Boser then caught Saint Preux with a knee and, two punches later, felled him with a right to the head. Referee Jason Herzog stepped in to stop the punishment at 2:31 of the round.
Boser (20-8-1) accepted the fight on short notice after Saint Preux's original opponent, Russian Maxim Grishin was unable to compete due to visa issues. Saint Preux (25-16-0) agreed to move up to heavyweight to face Boser, who had requested a quick return to action after a June 5 loss to Sweden's Ilir (The Sledgehammer) Latifi.