The WBA’s "champion in recess," Chagaev was ahead of Drumond on points when referee Gustavo Padilla stopped the bout after the sixth round. An accidental headbutt had opened a nasty cut over Chagaev’s swollen left eye, marring his vision.

Chagaev (25-0-1, 17 KOs) was taken to a hospital to treat the gash, and it was unclear how it would affect his upcoming schedule.

"It was a sad end to the fight," Chagaev said.

Drumond, from Costa Rica, kept trying to worsen the cut over Chagaev’s eye but could not find a knockout opportunity. Drumond lost for the first time in 27 fights in front of 4,000 fans at Stadthalle in this northern German port city.

Judges Hector Afu and Paul Thomas had Chagaev ahead 58-56, while Jean-Louis Legland had him ahead 60-54.

Chagaev was the WBA champion when he bowed out of a rematch with Nikolai Valuev because of a ruptured Achilles’ tendon. Valuev won the vacant title last August by beating John Ruiz, then defended it in December against former champion Evander Holyfield.

The 30-year-old Chagaev, because of his "champion in recess" status, must face Valuev by the end of June for the belt.

Chagaev won the WBA version of the title by beating Valuev in Stuttgart on 14 April 2007.