The Detroit Red Wings believe they upgraded their struggling second line Monday night, picking up Kyle Calder from Chicago for Jason Williams, in a swap of underachieving wingers.

A more significant improvement could come today, before the 3 p.m. NHL trading deadline.

The Wings are still heavily pursuing St. Louis Blues forward Bill Guerin, according to a source. As of Monday night, the asking price was too high. But, the Wings believe he won’t cost as much today. If the Blues don’t re-sign Guerin, they’ll have to trade him or risk losing him as an unrestricted free agent on July 1.

Guerin is one of several options for the Wings, who might also pick up a fourth-line grinder in addition to a goal-scoring winger. They still have enough money under the salary cap to acquire a player earning between $4 million and $5 million.

• Wings pick up Calder, pursuing Guerin