Seguin is believed to have developed the symptoms after a hit against the Chicago Blackhawks on Friday night. He was unavailable for practice on Saturday and then was unable to participate in off-ice activity on Sunday morning. This new development came shortly after Seguin missed two days of practice earlier in the week due to a muscle issue.
Ruff stated that the two injuries were not related, via The Dallas Morning News:
"He's day-to-day with concussion-like symptoms," Ruff said. "Earlier in the week, there was a muscle strain that we kept him off the ice for, but these two incidents are not related. It was just a hit that didn't seem like too much, but just caught him right, and he wasn't feeling good the next morning."
The coach also stated that the team followed league protocol in diagnosing the issue, with a team doctor evaluating, and subsequently ruling out Seguin on Sunday morning. Seguin is expected to travel with the team on a two-game road trip to Chicago and Toronto this week.