PHOENIX -- D-backs fans who were worried executive vice president and general manager Mike Hazen might be headed to Boston can rest easy.

On Friday, Hazen agreed to a contract extension with the D-backs on a deal of an unknown length.

The two sides had been negotiating on a new deal for around 10 days to two weeks, Hazen said, well before Red Sox president of baseball operations Dave Dombrowski was dismissed. D-backs CEO and team president Derrick Hall approached Hazen about an extension with the blessing of managing general partner Ken Kendrick.

“I’m extremely, extremely happy for our [baseball operations] group, and very appreciative,” Hazen said. “What Ken and Derrick did for us, I couldn’t be happier or more appreciative. What we’re trying to build here -- what I feel like we’ve started to build here -- is extremely important to all of us who work here. We want to see this through. We want to continue on this season, and seasons beyond, at building a sustainable winner and a World Series champion here.”

Hazen was initially signed by the D-backs to a five-year contract in October 2016 to replace Dave Stewart. Hazen had been the general manager of the Red Sox, but not the primary decision maker with Dombrowski holding the title of president of baseball operations.

“Mike and his staff have done a masterful job, and they have short and long-term plans here that are working towards building a sustainable winner,” Hall said. “He is one of the brightest and most innovative baseball minds in the game, and I am thrilled that he has chosen to remain a D-back regardless of outside opportunities.”

The Giants approached the D-backs last offseason about speaking with Hazen with regards to their GM opening, but Arizona denied permission as Hazen was not interested in leaving. Hazen is extremely loyal to his two closest advisors and assistant GMs, Amiel Sawdaye and Jared Porter.

Rather than instituting a complete teardown of the Arizona roster when he was first hired, Hazen decided to give the core of the team another chance to compete and instead made changes at the margins.

Right-hander Taijuan Walker and infielder Ketel Marte were acquired in a trade with the Mariners, and Hazen signed free agents such as closer Fernando Rodney and catcher Jeff Mathis.

Hazen also hired Torey Lovullo, who had been the bench coach of the Red Sox, to take over at manager for the D-backs in place of Chip Hale.

In one of the best Trade Deadline deals in recent memory, Hazen acquired slugger J.D. Martinez from the Tigers just after the All-Star break in 2017.

The D-backs beat the Rockies in the 2017 Wild Card Game before eventually falling to the Dodgers in the National League Division Series, with Lovullo named the NL’s Manager of the Year.

Martinez departed following the season via free agency, but Hazen once again put together a team that was near or in first place at the start of every month in 2018. A poor September saw Arizona fall out of the playoff chase and finish with an 82-80 record.

With the team set to lose left-hander Patrick Corbin and outfielder A.J. Pollock to free agency after the '18 season, Hazen looked to retool his roster rather than tear it down completely.

With that in mind, Hazen dealt franchise icon Paul Goldschmidt, who was one year away from free agency, to the Cardinals for catcher Carson Kelly, right-hander Luke Weaver, Minor Leaguer Andy Young and a 2019 compensation-round Draft pick.

Kelly has become a mainstay behind the plate and Weaver was one of the team’s best pitchers before an arm injury caused him to miss several months. Meanwhile, Christian Walker, who was a waiver pickup in Hazen’s first season, has proven to be an above-average replacement for Goldschmidt at first base.

At this year’s Trade Deadline, Hazen was able to deal Zack Greinke for four of the Astros' top prospects while only having to pick up about a quarter of the roughly $75 million left on Greinke's contract.

In addition, Hazen acquired right-hander Zac Gallen, who has pitched very well for Arizona, from the Marlins at the Deadline. He also picked up veteran Mike Leake from the Mariners.

The moves have been in keeping with Hazen’s philosophy of trying to compete, while at the same time building up the farm system. Arizona had seven of the first 75 picks in the 2019 MLB Draft and received positive reviews on its haul from most pundits.

Meanwhile, the Major League team has continued to be competitive, as they remain in contention for a Wild Card spot. That, though, is not enough for Hazen.

“We’ve added a base of talent to the organization that we didn’t have via trades ... via international signings, that we feel pretty good about,” Hazen said. “We’ve had a lot of really good performances at the Minor League level. We’ve had a lot of good, early indicators from the guys that we drafted just in this Draft. But that doesn’t mean anything until we translate it into wins at the Major League level. I’m not going to sit here and talk about farm system rankings and things like that. That’s not a marker, in my mind, for success. Success is winning Major League Baseball games year in and year out. As evidenced by our record, we’re not where we need to be.”

Hazen, though, felt like Arizona was where he wanted to be and the D-backs are happy that he’s staying.