Alvarez cracked a three-run, walk-off home run in the 11th inning Sunday for Double-A Corpus Christi.
The 20-year-old Alvarez, Houston's third-ranked prospect per RotoWire, is hitting .286 with two homers and 10 RBI through nine games. He entered the organization as a first base-only prospect, but the Astros began introducing him to left field in 2017, and he's started all nine games in left so far this season.