Sasaki's bullpen drew a crowd, as team officials, media members and even players watched the 23-year-old get to work.
Sasaki agreed last month to a minor league contract with a $6.5 million signing bonus as an international amateur free agent under Major League Baseball's rule.
Roki Sasaki has the talent to be an instant sensation the way Fernando Valenzuela or Hideo Nomo were in previous generations.