Kolosov turned aside 14 of 18 shots in a 5-1 preseason loss to the Bruins on Tuesday.
Kolosov entered Tuesday's preseason matchup in the first period after Dan Vladar exited due to an upper-body injury. While Kolosov wasn't particularly sharp, he could be Joseph Woll's backup at the start of the regular season if Vladar's injury forces him to miss time. Kolosov made 21 regular-season appearances for the Flyers across the past two seasons, going 5-11-1 with a 3.64 GAA and an .863 save percentage.