HOUSTON -- The Tigers activated outfielder Christin Stewart from the 10-day injured list Thursday and optioned him to Triple-A Toledo. The left fielder has been with the Mud Hens most of August on rehab assignments.

By remaining at Triple-A, Stewart will receive regular playing time, which he wouldn't necessarily have had with the Major League club. Tigers manager Ron Gardenhire also is looking for Stewart to make strides on defense.

"He's going to have to be better," Gardenhire said. "You can't continue to struggle and fight it. He's worked really, really hard, and he's better. But he still has to get better in the outfield and really be able to play [at Comerica Park]. Because our field is huge. And he's going to have to work on his throwing."

In 81 big league games this season, Stewart produced a .239/.321/.393 slash line, 21 doubles and seven home runs. He was placed on the 7-day concussion injured list on July 30. Stewart slashed .295/.392/.409 in 11 games with Toledo this month.

Boyd activated; Alexander optioned

After Thursday's game, the Tigers optioned left-hander Tyler Alexander to Triple-A Toledo and activated left-hander Matthew Boyd off the three-day paternity list. Boyd's wife, Ashley, gave birth to their son, Isaiah Robert Boyd, on Monday.

Boyd likely will start the series finale Sunday in Minnesota, though the Tigers have not announced that yet.

Alexander pitched four key innings of the Tigers' 2-1 win over the Astros on Wednesday. He entered the game in relief of Daniel Norris, who was on a three-inning limit, and held Houston to one run. Alexander walked one and struck out three in his extended outing.