Joe Joyce's hopes of early qualification for next summer's Olympic Games in Rio were dented as the British Lionhearts lost 4-1 to Russia in the World Series of Boxing.
The 29-year-old suffered a split-decision defeat against Maxim Babanin - his first loss of the campaign.
The fighters who finish top of each weight division automatically qualify for the Rio Games.
Britain's Joyce is currently second in the super heavyweight rankings.
Week 12 of the tournament had begun well, with Spain's Kelvin De La Nieve, who fights for the Lionhearts, beating Vasilii Vetkin in the flyweight contest.
But losses for Oualid Belaoura, Scott Fitzgerald, Joshua Buatsi and Joyce left the British team sixth in Group A.
The Lionhearts' final home contest of the season is against Cuba Domadores on Thursday, 16 April.
The return of a British franchise to the 16-team competition gives the British boxers the chance to gain fast-track qualification to the Games in Rio.
Last month, Liverpool's middleweight fighter Anthony Fowler missed the chance to qualify after he lost against Algeria's Ilyas Abbadi.