The deal, which was announced Monday, involves multiple players and required Segura to waive his no-trade clause to join Philadelphia.
Segura batted .304 with 10 home runs, 91 runs and 63 RBIs in 144 games last season and was named an American League All-Star.
In June 2017, Segura agreed to a five-year, $70 million contract with the Mariners spanning 2018 to 2022. The deal has a $17 million option for 2023, with a $1 million buyout.
Segura was the centerpiece of one of Seattle’s biggest moves after the 2016 season, when he was acquired from the Arizona Diamondbacks as part of a five-player trade.
He will become the latest high-profile player traded away by the Mariners, who are tearing down their roster in an effort to rebuild the team.
Santana, 32, signed a three-year, $60 million contract with the Phillies last offseason and has a base salary of $17 million in 2019 and $17.5 million in 2020. His contract has a club option for the 2021 season worth $17.5 million with a $500,000 buyout.
He hit .229 with 24 home runs and 86 RBIs in 2018.
The 23-year-old Crawford, drafted by the Phillies in the first round of the 2013 draft, hit .214 with three home runs and 12 RBIs in 49 games last season.