Olympic boxing hopeful Joe Cordina says allowing professional boxers to compete at the Olympics would be heartbreaking.
The change was voted by international boxing federations weeks before this year's games begin on 5 August.
The 24-year-old Commonwealth bronze medallist secured a place in Rio by beating David Joyce in the 60kg semi final at the European qualifiers.
"This time I've qualified. Imagine if they decided to bring someone else back to take my place," he told BBC Sport.
"It would be heartbreaking in the long run, if that does happen."
The International Boxing Association (AIBA) held the vote in Switzerland to allow professional boxers to compete at the Olympics.
Cardiff fighter Cordina fears the change could force amateur boxers out of contention to compete at the Olympics if professionals decide to enter.
"I went to a Commonwealth Games and I missed out on London 2012, which was disappointing, but I just knew that I needed to go an Olympic Games and this time around there was nothing stopping me," he continued.
"Imagine if people were waiting another four-year cycle for the next one. Even on the amateur circuit, coming in and taking your place, it's not a good feeling. It will break a lot of boys' hearts."
Forcing boxers out
Former world champions Carl Frampton and Ricky Hatton criticised the decision and Cordina believes that professionals coming into the Olympics could cause big changes in the way boxing works.
"Taking amateur boxing out of the Olympics, it'll end up being mainly pros who are making money and coming back just to go to an Olympic Games and taking people's spots," he added.
"At the minute, any top amateur boxing in the Olympic Games, they've obviously proved themselves and they're at the top of their game.
"I don't think they'll be too worried. In my gym we've got world champions and a British champion so I get a lot of sparring with pros and I hold my own with them."
Following the AIBA's vote, GB Boxing did not rule out sending professional boxers to the Olympics this year, if their two remaining qualification slots were not taken by amateurs while the British Boxing Board of Control (BBBC) objected to the proposal altogether.
"We will look at the decision to change the rules governing the eligibility of professional boxers competing in AIBA sanctioned competitions as part of our selection process," a statement from GB Boxing said.
"Selection for the final Olympic qualifier in early July will be based on the views of GB Boxing's Performance Team who will pick the boxer(s) whom they believe is/are most likely to be successful at the event and meet the qualification criteria for Rio."
However, the BBBC said, "It is the belief of the British Boxing Board of Control that such a move is against the spirit of the Olympics, disrespectful to the many GB Amateur boxers who, throughout the Olympic cycle compete around the world in qualifying tournaments and ultimately dangerous.
"It is the hope of the British Boxing Board of Control and many within the professional Sport in Great Britain and throughout the world that AIBA reconsider such a move that is not beneficial to the Sport as a whole."