Williams also had nine assists and seven rebounds in the Thunder's 127-113 victory on Sunday (Monday AEDT).
Australian Josh Giddey had a relatively quiet match, making five rebounds and four assists and scoring five points during his 20 minutes on court.
Malik Monk led the team with 26 points.
Sacramento's leading scorer De'Aaron Fox was held to 15 points on six-for-17 shooting.
The Celtics have won all three match-ups with the Heat this season and have won six of the past seven games against them.
Miami were without leading scorer Jimmy Butler, who was granted a leave of absence because of the death of a family member.
The Heat rallied from a 15-point deficit in the third quarter and cut it to 106-104 on Herro's three-pointer with one minute 49 seconds remaining.
But Porzingis and Tatum each converted two free throws to secure the win.