Veteran goaltender Jaroslav Halak might be the change the Blues need to get back on track.
Halak will try to help St. Louis win its fifth straight over the Edmonton Oilers on Saturday night.
With the Blues (16-11-2) going for a fourth consecutive victory, Allen, who has at least for now taken over the No. 1 job from Halak and Brian Elliott, allowed three second-period goals in Tuesday's 3-2 loss at Vancouver.
"We played a good 40 minutes, but the other 20 minutes cost us the game," said center Patrik Berglund, who tied Chris Stewart for the team lead with his 14th goal.
Coach Ken Hitchcock deciding to give Halak his first start in five games could give the Blues their best chance to win on Saturday. He has been in net each time during St. Louis' winning streak over Edmonton, posting a 1.75 goals-against average, and stopped 15 shots in a 4-2 home win March 1.
Halak will face an Oilers club that's worked its way back to the fringe of the crowded Western Conference playoff picture with a 3-0-2 stretch. Edmonton (11-11-7), though, is coming off a 4-3 shootout loss to San Jose on Wednesday in a game it led 3-1 in the third period.
"It's painful, but we have to look at the fact that we have points in five games and move forward," said coach Ralph Krueger, whose team is seeking its first postseason berth in seven seasons.
The Blues have dropped five of seven on the road, but they're 8-3-3 in their last 14 at Edmonton following a 5-2 victory last Feb. 29.
Center Andy McDonald, who scored twice in that victory, will face the Oilers for the first time this season after returning from a 10-game injury absence (knee) on Tuesday.
Blues center T.J. Oshie is expected to play after missing the last three contests with a rib injury. He set up Jaden Schwartz and captain David Backes for goals in the win over Edmonton earlier this month as St. Louis rallied from two down after 20 minutes.
The Oilers could have center Ryan-Nugent Hopkins back after he missed Wednesday's game with the flu. The former No. 1 overall pick is tied for 11th on the club with two goals.
Center Sam Gagner, the team leader with 12, has five goals and two assists in a five-game point streak. He has totaled one assist in the losing streak to St. Louis.
Stewart, the NHL's first star of the week, has two goals and three points in that stretch after setting up Kevin Shattenkirk's game-tying goal on March 1.
Devan Dubnyk turned aside 26 shots in that game as his career record versus St. Louis fell to 0-7-0 with a 4.72 GAA. He's started Edmonton's last 11 games.
The Blues are 10-1-1 in the last 12 in this series, which continues Tuesday in St. Louis.