Souza hurt his shoulder in a collision with the right-field wall and left Friday night's game. He appeared as a pinch-runner on Saturday night.
Taylor will make his major league debut less than a week after being promoted to Syracuse. He hit .315 with 22 homers, 63 RBIs and 35 stolen bases for Double-A Harrisburg and represented the Nationals in the Futures Game.
The Nationals needed help for their outfield. Nate McLouth (right shoulder inflammation) is on the 15-day DL. Right fielder Jayson Werth has not started in the last two games due to a sore right ankle and right shoulder.