The Astros placed Matthews on the 10-day injured list Friday with a left knee sprain.
In a corresponding move, the Astros selected Lucas Spence's contract from Triple-A Sugar Land, and Spencer will man center field in his major-league debut Friday against Baltimore. Matthews was injured in the Astros' final game before the All-Star break. He's hitting .197 with seven homers, 22 RBI, 23 runs scored, four stolen bases and a 15:71 BB:K across 226 plate appearances this season.