In practice for the last two days, Sam Gagner has taken line rushes in Draisaitl's spot on the second line. The fact the Oilers didn't replace Draisaitl's spot with a more permanent solution suggests that Gagner was just acting as a placeholder, and the Oilers are expecting Draisaitl to be able to play.
Oilers fans know that Leon Draisaitl is a machine in the playoffs, and will play through an injury if it's at all possible. A few years ago, Draisaitl played the best playoff hockey of his career with a high ankle sprain, barely moving around the ice but still finding a way to be an elite player. As long as Draisaitl's in the lineup, he and the Oilers will find a way to finally beat the Canucks for the first time this year.