Hofer gave up five goals on 21 shots before being replaced by Jordan Binnington midway through the second period in Tuesday's 8-1 loss to the Senators.
Neither goalie got much help from their defense in the rout, and the last two goals against Hofer came on Ottawa's power play. It's the first loss of the season for the 24-year-old netminder, who's posted a 3-1-0 record with a 3.40 GAA and .903 save percentage through four appearances as the Blues' No. 2 goalie.