Whiteside, 30, has one year remaining on his current contract after exercising his $27.1 million player option two weeks ago. Leonard and Harkless also are in the final year of their contracts.
Whiteside, who was named to the second team All-NBA defensive team in 2016, averaged 12.3 points and a Heat-best 11.3 rebounds per game last season in 72 regular-season contests. He averaged only 23.3 minutes per game and previously expressed his displeasure at his limited role with the team, according to ESPN.
The Sacramento Kings selected Whiteside in the second round (No. 33 overall) of the 2010 NBA Draft out of Marshall. The franchise waived him on July 16, 2012.
In parts of seven seasons with the Sacramento Kings and the Heat, Whiteside has averaged 13.4 points and 11.4 rebounds. He led the NBA in blocks per game during the 2015-16 campaign and topped the league in rebounds the next season.