Lionell Thompson came close, but the Buffalo light heavyweight suffered a controversial loss to unbeaten Radivoje Kalajdzic on Saturday night.

Thompson, who was penalized a point by the referee during the fight for a mouthpiece violation, dropped a split decision to the hard-hitting Serbian (15-0, 10 KOs), 78-72, 75-77, 76-75, in a fight shortened to eight rounds due to time contraints at Boardwalk Hall in Atlantic City, N.J. The bout was part of the undercard of Saturday night’s Sergey Kovalev-Cedric Agnew world championship fight on HBO but wasn’t televised.

According to Thompson’s manager Tim Ziccardi, Thompson was penalized when the referee ruled he spit out his mouthpiece in the sixth round, although Thompson’s camp says it was knocked out of his mouth by a punch. Thompson, who fights for Main Events, may file a protest with New Jersey Athletic Commission.

The loss somewhat blunts some of the momentum the 28-year-old has gained in the past 16 months that has seen him go from after-thought to a potential player in the light heavyweight division. Thompson (15-3, 9 KOs) entered the fight ranked eighth by the World Boxing Association and 14th by the World Boxing Council. He had strung together three straight wins since losing to now-world champion Kovalev back in September 2012 as a last-minute fill-in in a fight he probably should not have taken.

Thompson’s other loss was a controversial one in Quebec to French-Canadian Nicholson Poulard via split decision for the NABA title.

In another undercard fight, Buffalo heavyweight Excell Holmes fell to 2-3-1 as he was stopped in the second round by unbeaten Adam Kownacki (6-0, 6 KOs).