David Nalbandian was disqualified from the Aegon Championships final after injuring a line judge by kicking an advertising board into his shin.
The Argentine, 30, was leading Marin Cilic 7-6 (7-3) 3-4 when he smashed a panel in front of Andrew McDougall's seat, causing his leg to bleed heavily.
Chair umpire Fergus Murphy awarded Cilic the match, while ATP supervisor Tom Barnes confirmed the decision.
"I am very sorry, sometimes you get frustrated on court," said Nalbandian.
With the officials discussing what course of action to take, sections of the 6,000-capacity crowd booed and chanted "play on".
But the match was abandoned and Nalbandian was left to explain his behaviour to Sue Barker on BBC One.
"Sometimes I make a mistake I agree with," he added. "It's a tough moment to end a final like that but sometimes we feel so much pressure from the ATP playing so many tournaments.
"Today I've made a mistake. Sometimes I agree and I do but everyone makes mistakes. I don't feel it had to end like that - especially in a final.
"There are a lot of rules and sometimes they don't do anything. The rule book is very big and I can tell you the ATP do a lot to the players and nothing happens."
After edging the first set on a tie-break, Nalbandian's serve was broken in the opening game of the second.
He managed to level at 3-3 but immediately handed the advantage back by putting a forehand wide on the stretch.
The world number 39 continued his run before angrily booting the board, which broke apart and badly gashed McDougall's left leg.
He received immediate treatment from St John's Ambulance and saw the tournament medical team, but no further treatment was required.
"It is unsportsmanlike conduct, and the supervisor has the authority to declare an immediate default," said Barnes. "Once I saw that the line judge was injured, I didn't have any other option."
Tournament official Chris Kermode later said: "It is obviously not the way that we wanted to finish the final and I can understand the crowd's frustration.
"But the tournament is governed by ATP rules and this was a clear-cut case.
"The line judge was seen and treated by St John's Ambulance. He also saw the doctor, and no further treatment was required."
Rule 8.04 of the ATP rule book states a player guilty of aggravated behaviour can expect to be fined "up to $25,000 or the amount of prize money won at the tournament, whichever is greater".
Given that the runners-up prize money at Queen's is 44,945 euros (£36,114), Nalbandian stands to lose more, as well facing a fine of up to $10,000 (£6,365) and forfeiting the ranking points he earned.
He was appearing in his first grass court final since Wimbledon in 2002.
"It was very bitter," said the sixth seed. "It's definitely not the way I wanted to win. To end like this is not easy.
"The match was getting hot and it's tough to see the final finish like this. I can't change it, but I'm really sorry for the fans that it finished like this."
In the doubles, top seeds Max MirnyiandDaniel Nestor of Canada comfortably beat the Bryan brothers, Bob and Mike, 6-3 6-4.