Steen opened the scoring in the first period Thursday against the New York Rangers with his team-leading 26th goal, but a lower-body injury kept him from finishing the 2-1 victory that helped St. Louis (34-11-5) bounce back from a 7-1 loss at New Jersey two nights earlier.
"We'll see where he is in a day or so," Blues coach Ken Hitchcock told the NHL's official website after his team improved to 2-1-0 on the trip. "He'll be back."
Among the league's top goal-scorers, Steen has two and two assists in four games since he missed 11 with a concussion. The Blues went 8-2-1 during that stretch without him.
"Anytime you lose a guy like Alex Steen it's tough. He's been our guy this year," said St. Louis defenseman and New York native Kevin Shattenkirk, who scored the eventual winner on a power play early in the third Thursday.
"We did a great job last time he went out of the lineup. Hopefully it's not too long. We'll have to wait and see."
Despite Steen's injury, the Blues should have some confidence moving forward.
Though St. Louis has been held to one or two goals in six of seven games, it kept the Rangers off the board on three power-play chances after allowing at least one in three consecutive games, including three against the Devils.
The Rangers had 28 shots through the first two periods but were limited to seven in the third. St. Louis got 34 saves from Jaroslav Halak, who allowed four goals in relief of Brian Elliott at New Jersey, but is 4-1-0 with a 1.21 goals-against average as a starter this month.
"I'm really happy with the way the night went," said Shattenkirk, who has scored two of his eight goals in the last three games.
Shattenkirk had two assists and Halak made 22 saves as the Blues posted their second straight 5-1 victory over the Islanders (21-25-7) at home Dec. 5.
The Islanders have recorded 16 non-shootout goals but allowed 18 while splitting their last four contests. Michael Grabner had a goal with an assist Thursday against Pittsburgh but the Islanders blew an early 2-0 lead en route to a 6-4 home loss, their fourth defeat in 14 games.
"Again, it was about our battle level or the lack of it," coach Jack Capuano said. "We have to defend harder. We got away from how we have to play for about 10 minutes and it cost us."
Kyle Okposo scored his second goal in three games, and has six points in the last four for the Islanders. He assisted on Andrew MacDonald's power-play goal at St. Louis last month.
Teammate John Tavares has two goals with five assists during a five-game point streak, but he's been held without a point in two straight and four of five career contests against the Blues.