Backes did not participate in St. Louis' morning skate, but coach Ken Hitchcock did not rule him out for the game. The final word came when Backes was on the list of scratches on the pregame roster report.
Forward Brenden Morrow also was scratched after Hitchcock said earlier in the day that he would miss the rest of the series. Morrow missed the final three games of the regular season with a foot injury. He played in Games 1 and 3 against the Blackhawks.
Backes also missed Game 3 after he absorbed a big hit from Blackhawks defenceman Brent Seabrook in the third period of St. Louis' 4-3 overtime victory Saturday. The captain was helped off the ice and did not return.
Seabrook received a major penalty and game misconduct for the hit, and was suspended for three games by the NHL.
While the Blues were without Backes and Morrow, centre Derek Roy returned after missing St. Louis' 2-0 loss in Game 3. Roy had an assist on Jaden Schwartz's tying goal in the third period of the Blues' 4-3 triple-overtime victory in the series opener.