Merilainen was recalled from AHL Belleville on Saturday.
Merilainen was sent to AHL Belleville on Friday.
Merilainen stopped nine of 12 shots before being replaced by Mads Sogaard early in the second period of Thursday's 7-2 loss to the Panthers.
Merilainen will be between the visiting pipes in Florida on Thursday, Wayne Scanlan of the Ottawa Citizen reports.
Merilainen stopped 34 of 37 shots in the Senators' 3-2 overtime loss to the Hurricanes on Tuesday.
Merilainen was the first goalie off the ice at the morning skate, TSN 1200 Ottawa reports, indicating he will start in Carolina on Tuesday.
Merilainen was summoned from AHL Belleville on Sunday.
Merilainen signed a three-year, entry-level deal with Ottawa on Monday, CapFriendly reports.
Merilainen was drafted 71st overall by the Senators at the 2020 NHL Entry Draft on Wednesday.