Pirin Gotse Delchev goalkeeper Abdi Abdikov was sent off for hitting a team mate during his club's 5-1 loss at Cherno More Varna in the Bulgarian league on Sunday.
The 29-year-old keeper thumped left back Atanas Fidanin midway through the first half with referee Dimitar Andreev having stopped the game to allow players to drink some water in the scorching temperatures.
"It's something that I have seen for the first time in my career as a player and a coach," Pirin coach Tencho Tenev told a news conference. "To be honest, I didn't follow the match after that.
"I have no explanation why he did it. Well, we made a mistake and they scored a goal but this is completely unacceptable."
Fidanin was not injured in the incident and continued to play while Abdikov could face a three-match ban from the Bulgarian Football Union.
Pirin, who were promoted to the Bulgarian top flight for the first time last season, hit the headlines in August when coach Yakov Paparkov quit a few minutes after the team won their opening match. [ID: nL4E8JC0A0]
Pirin, based in Gotse Delchev - a southern town with a population of 20,500 - are 10th in the standings with 27 points from 24 matches, six points above the relegation zone. Cherno More are 11th with 24 points.