"I flat-out told them, 'I want to be here,'" Sale said during his press conference Saturday.
The deal, reportedly worth $145 million, includes an opt-out clause after the 2022 season and an unspecified amount of deferred money, according to Ken Rosenthal of The Athletic.
Additionally, the contract contains a sixth-year vesting option based on games started that would be worth at least $20 million, sources told Jeff Passan of ESPN. It also features escalator clauses in each of the final four guaranteed years and the 2025 option based on where Sale finishes in Cy Young voting, Passan reports.
* Sale can opt out of season
** Vesting option
Breakdown courtesy: Ken Rosenthal
Sale also receives a full no-trade clause that will take effect partway through the 2020 season, according to Passan.
The contract will go into effect following the 2019 campaign, during which Sale is owed $15 million.
"I think it's pretty fair for both sides. That's why I signed it," Sale said.
In two seasons with the Red Sox since being traded from the Chicago White Sox in a blockbuster involving Yoan Moncada and Michael Kopech, Sale posted a 2.56 ERA and 2.25 FIP over 59 starts, finishing in the top four of American League Cy Young voting both years.
The 29-year-old played an integral role in Boston's 2018 championship season, most notably coming out of the bullpen to record the final outs of Game 5 in the World Series.
"We win. We have a track record of winning," Sale said. "Even when we don't, we're lined up to win."
The Red Sox were rumored to have been working on a contract extension with reigning AL MVP Mookie Betts. However, the outfielder said on Wednesday that he'll likely wait for free agency, while team president Dave Dombrowski recently stated he won't negotiate contracts once the season begins on March 28.