The Houston Astros and free agent first baseman Christian Walker have agreed to a three-year, $60 million contract, sources confirmed to ESPN amid multiple reports Friday.

The deal is pending a physical exam, a source told ESPN.

The addition of Walker in all likelihood marks the end of Alex Bregman's tenure in Houston, not to mention the Astros' ill-fated attempts to pry Nolan Arenado from the St. Louis Cardinals. Walker manning first base for the next three years means Isaac Paredes, the 25-year-old corner infielder who was recently acquired from the Chicago Cubs in the Kyle Tucker trade, will probably be Bregman's replacement at third base.

Walker, who turns 34 on March 28, is widely regarded as one of the sport's best defensive first basemen and will also provide some power to the middle of the Astros' lineup. He slashed .250/.332/.481 with 95 home runs and 281 RBIs with the Arizona Diamondbacks over the past three seasons while accumulating 10.8 FanGraphs wins above replacement, sixth-most among first basemen.

First base had been a conundrum in Houston over these past three seasons, one the high-priced Jose Abreu could not solve. Astros first basemen combined for a .651 OPS last season, fifth-lowest in the majors. Walker, a three-time Gold Glove Award winner, will provide a major boost at that position -- particularly as a right-handed hitter in Daikin Park, which features a short left-field fence.

The Astros still need help in their outfield after parting with Tucker one year before he's scheduled to become a free agent. And Bregman, the heart and soul of a Houston franchise that won two championships and made seven straight appearances in the American League Championship Series dating back to his first full season in the big leagues, must choose a new destination.

The New York Yankees, who expressed interest in Walker this offseason, could be a landing spot for Bregman. So might the Boston Red Sox, Toronto Blue Jays or Detroit Tigers, the last of which is led by AJ Hinch, Bregman's former manager.

Astros general manager Dana Brown expressed optimism about bringing Bregman back throughout the offseason, but owner Jim Crane would not meet the $200 million-plus asking price of Bregman's agent, Scott Boras, prompting an initial pivot to Arenado -- before he used his no-trade clause to stay in St. Louis -- and an agreement with Walker.

Walker declined the D-backs' qualifying offer in November. By signing him, the Astros, a team that exceeded the luxury tax threshold last season, will give up their second- and fifth-round picks in the upcoming draft, as well as $1 million from their international spending pool. Houston will get back a fourth-round pick once Bregman signs with another team, a development that now feels inevitable.

In the aftermath of the Astros' loss to the Tigers in the wild-card round earlier this fall, longtime Houston second baseman Jose Altuve spoke passionately about the importance of bringing Bregman back, saying: "We're not going to be the same organization without him."

In many ways, the Walker signing signals a new chapter.