Blues coach Ken Hitchcock disclosed his decision Monday.
Halak was injured in the second game of the Blues' first-round series against San Jose, leaving with an undisclosed lower-body injury that is believed to be a sprained left ankle he suffered during a collision with teammate Barret Jackman. He appeared to be walking fine leaving the locker room after the first-round clincher but was not at practice Monday.
Hitchcock had little to say about Halak's progress, aside from the fact there had not been a setback.
"Jaro's not going to be around for the first two games, and then we'll see from there," Hitchcock said.
St. Louis had the deepest goalie tandem in the NHL this season. Brian Elliott led the NHL with a 1.56 goals-against average, including nine shutouts.
The NHL has not yet announced specific dates for the Blues-Kings series.
Information from The Associated Press was used in this report.