Forward Nikita Alexandrov (left) and defenseman Tyler Tucker of the St. Louis Blues. (Jeff Curry/USA TODAY Sports)

In response to forward Robert Thomas' early exit from Thursday night's loss to the Coyotes in Arizona, the St. Louis Blues swapped a defenseman for a forward with a pair of roster moves on Friday.

The Blues recalled forward Nikita Alexandrov from Springfield, their AHL affiliate, and assigned defenseman Tyler Tucker to the Thunderbirds.

Tucker, who has played in 12 games with the Blues as a rookie this season, became a movable piece with the recent return of several injured defensemen -- Torey Krug, Nick Leddy and Robert Bortuzzo (although Bortuzzo has yet to play since coming off injured reserve). But the Blues' needs up front increased when Thomas left the game Thursday early in the second period with a lower-body injury after absorbing an Arizona shot. He did not practice with the team Friday morning.

Coach Craig Berube said Friday that Thomas remains sore and is day-to-day. "He'll stay on the trip with us and see when he can be available," he said.

Thomas' absence, should it come to that, would pose a problem for a Blues team that was blanked 5-0 by the Coyotes and has lost three straight games to teams not currently in the playoff picture. Thomas leads the Blues with 31 assists and is second in points with 43.

Alexandrov, 22, is back for his third stint with the Blues this season. He has four points (two goals, two assists) in 16 games with St. Louis as well as 20 points (12 goals, eight assists) in 23 games with the Thunderbirds.

"We need a center, losing a guy, Robby," Berube said. "He played pretty good for us when he was up here. He's pretty detailed and gets pretty involved physically and decent puck skills."

The Blues will play at Colorado on Saturday and at Winnipeg on Monday heading into the NHL All-Star break.