Manoah, in his second MLB season, was 16-7 with a 2.24 ERA this year and was named to the American League All-Star team.
The former first-round pick was at his best in September, going 4-0 with a 0.88 ERA in six starts.
Manoah lost his only start against the Mariners this year -- also a 2-1 defeat on July 9. He gave up two runs on three hits in 7.1 innings.
The Mariners have not yet named a starter.
Speaking before a season-ending doubleheader against the Baltimore Orioles, Blue Jays interim manager John Schneider said the team is still working through its options for Game 2 of the playoff series.
Meanwhile, Schneider said outfielder Lourdes Gurriel Jr. (hamstring) and infielder Santiago Espinal (oblique) have been sent back to Toronto to take some live batting practice and work through infield drills under the Rogers Centre roof ahead of this weekend’s wild-card series
The best-of-three series runs Friday through Sunday with all games in Toronto.