Frolik was cut loose from his professional tryout with the Blues on Thursday.
Frolik signed a professional tryout offer with the Blues on Friday.
Frolik ascended from the taxi squad and will play Wednesday's game against the Oilers, Arpon Basu of The Athletic reports.
Frolik was assigned to the taxi squad Thursday, per CapFriendly.
Frolik recorded one assist and one hit over 10:04 of ice time in Wednesday's 4-1 loss to Toronto.
Frolik was assigned to the active roster for Wednesday's game against Toronto, per CapFriendly.
Frolik was assigned to the taxi squad Saturday, per CapFriendly.
Frolik had one shot and three hits over 11:46 of ice time in Tuesday's 4-0 win over Edmonton.
Frolik will be in the lineup Tuesday against the Oilers, Stu Cowan of the Montreal Gazette reports.
Frolik was designated for the taxi squad Wednesday, per CapFriendly.