CHICAGO -- Chicago Blackhawks defenseman Kimmo Timonen was ruled out of Sunday's game against the St. Louis Blues after suffering an undisclosed injury in the first period.

Timonen, 40, left the game shortly after he was hit into the boards headfirst by the Blues' Ryan Reaves at 9:28 of the first period. Timonen played three shifts in the first period.

Blackhawks coach Joel Quenneville said after the 2-1 loss that Timonen is day-to-day with an upper-body injury.

Timonen didn't play his first game this season until March 2 due to blood clots, which were discovered in the summer. He was acquired by Chicago from the Philadelphia Flyers on Feb. 27. He has appeared in 16 games for the Blackhawks. He previously announced he plans retire after this season.