Middleweight champion Gennady Golovkin of Kazakhstan has now knocked out 15 consecutive opponents after stopping Curtis Stevens of Brooklyn after eight rounds in a title defense Saturday at Madison Square Garden. Golovkin has not had to go the distance in a fight since June 2008.

Golovkin decked Stevens in the second round with back-to-back left hooks to the head. Golovkin had done serious damage to the body and head over the rest of the fight, Stevens’ corner finally telling the referee it wanted the fight stopped after Stevens had absorbed tremendous punishment in the eighth.

Golovkin, who is trained by West Covina’s Abel Sanchez in Big Bear, is now 28-0 with 25 knockouts and continues to hold the record for best knockout ratio (89.2 percent) of any middleweight champion in history.

Afterward, Golovkin called out fellow world champions Sergio Martinez and Peter Quillin when being interviewed by HBO analyst Max Kellerman.

Stevens (25-4) showed plenty of courage during the bout, and certainly