Pillar spent one year with the Giants after being acquired from the Toronto Blue Jays early in the 2019 season.
"It was a difficult decision. It was a baseball decision, not a financial decision," Giants president of baseball operations Farhan Zaidi told Alex Pavlovic of NBC Sports Bay Area. "We want to make sure that we can provide the opportunity to some of our younger outfielders who have emerged over the last year."
The 30-year-old is known primarily for his glove but was worth minus-5 defensive runs saved in center field following the trade. However, Pillar did surprise at the plate, slashing .259/.287/.432 with a career-best 21 homers and 87 RBIs while leading the Giants in multiple offensive categories.
For his efforts, Pillar finished 22nd in NL MVP voting after garnering one 10th-place vote. He also won the "Willie Mac Award" as the Giants' most inspirational player.
The Giants also non-tendered left-hander Tyler Anderson, right-hander Rico Garcia, and outfielder Joey Rickard. Outfielder Alex Dickerson, infielder Donovan Solano, and left-hander Wandy Peralta, meanwhile, all agreed to contracts with the team and avoided arbitration.