Doing the same were two Cuban outfielders who have been major disappointments and spent all of this season in the minor leagues: Boston's Rusney Castillo and Arizona's Yasmany Tomas.
Heyward keeps the $184 million, eight-year deal that pays him $106 million in the next five seasons. The others all have two years left in their contracts: Melancon is owed $28 million, Tomas $32.5 million and Castillo $24.5 million.
They all had to make their decisions by Wednesday night.
The 29-year-old Heyward, who in 2016 helped the Cubs to their first title in 108 years, hit .270 with eight homers and 58 RBIs in 127 games this season. He is owed $20 million in 2019, $21 million in each of the following two seasons and $22 million apiece in the final two years. If he has 550 plate appearances next year, he would again have the right to void the deal and become a free agent.
Melancon, 33, was 1-4 with a 3.23 ERA and three saves in 41 relief appearances, allowing 11.1 hits per nine innings for the second straight year and a .302 opponents' batting average in 2018. He has made 73 appearances in the first two seasons of a $62 million, four-year deal and is due $14 million in each of the final two seasons.
The 31-year-old Castillo has appeared in just 99 games since agreeing in August 2014 to a $72.5 million, seven-year contract and has not played in the major leagues since he was sent outright to the minors on June 20, 2016.
He hit .319 with five homers and 59 RBIs for Triple-A Pawtucket this year and is owed $11 million next year and $13.5 million in 2020. By keeping him in the minors, the Red Sox ensured his salary would not count on their luxury-tax payroll; under a change made after the 2016 season, he would count if he were brought up and sent outright to the minors again.
Tomas, who turns 28 this month, was sent outright to the minors April 2 and hit .262 with 14 homers and 65 RBIs for Triple-A Reno. His $68.5 million, six-year deal calls for $15.5 million next year and $17 million in 2020.