Former IBF flyweight champion Amnat Ruenroeng of Thailand won his first bout Monday at an Olympic qualifying tournament in Vargas, Venezuela.
U.S. contenders Cam F. Awesome, Paul Kroll and Brandon Lynch lost their opening bouts, failing to earn spots at the Rio de Janeiro Olympics next month.
The 36-year-old Ruenroeng fought at the Beijing Olympics, falling one win shy of a medal. Four years after mounting a successful professional career, he is one of just two moderately prominent pro boxers attempting to take advantage of the International Boxing Association's (AIBA) decision to allow pros to compete in the Olympics by jumping into the final qualifying tournament before Rio.
Ruenroeng won his bout in Venezuela against Germany's Artur Bril, who fights in an AIBA-backed professional league. Ruenroeng lost his IBF title less than six weeks ago when John Riel Casimero stopped him.
Awesome lost a decision to Ecuadorian heavyweight Julio Cesar Castillo Torres, who also beat him at the previous Olympic qualifying tournament in Azerbaijan last month. Awesome is a four-time U.S. national champion and a two-time Olympic trials champion, but he missed his first Olympic shot four years ago when he failed to complete his drug tests while still fighting under his birth name, Lenroy Thompson.
''Lost my fight today and now my Olympic run is over,'' the 27-year-old Awesome said in a post on his Twitter account. ''Time to re-re-reinvent myself and see what's next for me. It may not be boxing.''
Awesome has expressed skepticism about becoming a professional, preferring the Olympic-style version of the sport.
Kroll also lost a 3-0 decision to Germany's Arajik Marutjan in a welterweight bout, ending the Philadelphia-based fighter's Olympic hopes.
Lynch lost a decision to Ukraine's Rostyslav Arkhypenko in their super heavyweight bout.
Six American men and two women have qualified for Rio, but that could be the full extent of the team representing the U.S., the most successful nation in Olympic boxing history.
While Claressa Shields won a gold medal and Marlen Esparza earned a bronze during the debut Olympic women's boxing tournament in London, the U.S. men won no medals in 2012 and just one bronze medal in 2008. Andre Ward is the last American man to win a gold medal, although the current team has legitimate medal hopes with bantamweight Shakur Stevenson and flyweight Antonio Vargas.
U.S. light heavyweight Jonathan Esquivel beat Bulgaria's Spas Genov in his opening bout in Venezuela, but Esquivel's path to Rio is now blocked in his next bout by 32-year-old Hassan N'Dam. The French-Cameroonian fighter who briefly held two versions of an interim middleweight title is attempting to earn another trip to the Olympics after losing in the quarterfinals in Athens 12 years ago.
Ruenroeng and N'Dam are the only significantly accomplished pros attempting to win this final qualifying tournament for the Rio Games under the AIBA rule change, which has drawn widespread condemnation from many fighters and coaches.
After drawing initial interest from several pros including Manny Pacquiao and Wladimir Klitschko, AIBA's gambit apparently has failed to attract any big-name boxers into the field. Most boxing observers believe more prominent pros will fight at the 2020 Olympics in Tokyo.