"Several years ago, I promised our loyal fans that I would do everything in my power to bring a world championship team to our city. I will never waver from that commitment," Phillies managing partner John Middleton said in a statement.
Middleton added: "With the knowledge that I have gained from my evaluation, combined with the personal reflection on the 2019 season, I have decided that some changes are necessary to achieve our ultimate objective. Consequently, we will replace our manager. I am indebted to Gabe for the steadfast effort, energy, and enthusiasm that he brought to our club."
Kapler posted a 161-163 record across two seasons with the Phillies, failing to make the playoffs despite overseeing a roster that consisted of Rhys Hoskins, Aaron Nola, and Jake Arrieta for both years and added Bryce Harper last offseason.
"I am grateful to John, the Buck family, Andy (MacPhail), Matt (Klentak) and the entire Phillies organization for giving me the opportunity to lead this team for the last two years, Kapler said in a statement. "We came into 2019 with very high hopes. We fell short of those, and that responsibility lies with me."
Philadelphia is expected to hire a new manager with prior big-league experience, according to MLB Network's Jon Morosi, who named Dusty Baker and Buck Showalter as ex-skippers with connections to Phillies president MacPhail.
The Philles are the eighth team with a current managerial opening, joining the Angels, Cubs, Giants, Mets, Royals, Padres and Pirates.
Along with Kapler's firing, the Phillies announced that pitching coach Chris Young will not return in that position in 2020 and hitting coach Charlie Manuel will resume his role as a senior advisor to the general manager.
The remainder of the Phillies' coaching staff has been invited to return next season.