Porter, who lives in the Houston area and is in his second season as third-base coach for the Nationals, declined to comment. He was picked up at the airport by Astros owner Jim Crane.
Porter, 40, has interviewed for managerial jobs previously, mostly recently with the Marlins in the middle of the 2010 season after they dismissed Fredi Gonzalez.
Prior to joining the Nationals, Porter was the third-base coach for the D-backs for one year, and later served briefly as bench coach in Arizona under Kirk Gibson.
The Astros began interviewing managerial candidates this week in an effort to find a full-time manager. Brad Mills was let go last month after nearly three years at the helm of the club, and Tony DeFrancesco has been managing the club on an interim basis.
Porter played three seasons in the Major Leagues with the Cubs, A's and Rangers. He began his coaching career in 2005 as the hitting coach for Class A Greensboro, and later served as manager at Class A Jamestown in '06. He was the Marlins' third-base coach and baserunning instructor from '07-09.