Gallen threw 75-to-80 pitches in a simulated game at Angel Stadium in Anaheim on Tuesday, Nick Piecoro of the Arizona Republic reports.
Gallen had his final tuneup session in advance of an expected start Sunday against the Padres. The Diamondbacks are working their way down the coast for Friday's Opening Day. After two exhibition games in Los Angeles, the club is working out in Anaheim and will move on to San Diego.