DAVIE, Fla. -- Former IBF light heavyweight champion Glen Johnson stopped Yusaf Mack at 2:21 of the sixth round Friday night.
Fighting for the first time since losing a decision against Chad Dawson in November, Johnson shook off a sluggish first two rounds and gradually wore down Mack in the scheduled 12-round bout at the University Center.
Johnson (50-13-2, 34 KOs) knocked down Mack (28-3-2) three times in the sixth, with the final one ending the fight.
The win earns Johnson, of Jamaica but now living in Miami, a mandatory title fight against IBF champion Tavoris Cloud.
Mack, of Philadelphia, moved in angles and was effective at landing lead left jabs and rights to the head in the early rounds. But Johnson remained intent on keeping the fight at short range.
Early in the third round, Johnson found his opening and pinned Mack to a corner, where he scored with repeated rights to the head.
Johnson weighed in at 173 pounds and Mack came in at 175.
In another bout, two-time Olympic gold medalist Guillermo Rigondeaux of Cuba knocked out Mexico's Adolfo Landeros 28 seconds into the first round.