The Astros welcomed first baseman Christian Walker to the team in one of two moves that almost certainly marks the end of Alex Bregman’s time in Houston. Walker signed a three-year contract that will pay him $20 million annually just more than a week after the Astros acquired infielder Isaac Paredes from Cubs in the trade that sent outfielder Kyle Tucker to Chicago. “The way I view it right now is Paredes is going to play third base and Walker is going to play first base,” general manager Dana Brown said. “And Bregman’s still a free agent.” The Astros had hoped to re-sign Bregman, the team’s third baseman for the last nine seasons, but Brown said the negotiations had stalled.