Mateo experienced a loss of smell and taste but is starting to feel better, Tingler added.
The Padres acquired the 25-year-old from the Oakland Athletics on June 30 for a player to be named later.
Mateo is the Padres' 13th-ranked prospect, according to MLB Pipeline.
The Athletics traded for Mateo in the deal that sent Sonny Gray to the New York Yankees.
Though Mateo has yet to crack the majors, he's coming off a very strong season in Triple-A. He hit .289/.330/.504 with 19 home runs, 95 runs scored, and 24 stolen bases in 119 games with the Las Vegas Aviators in the Pacific Coast League.