The St. Louis Blues announced on Monday, that forward Jori Lehtera underwent ankle surgery on August 4th, repairing damage done late last season, after blocking a Duncan Keith slap shot. Lehtera was hoping to have the injury heal in the rest he got in the off-season, but after returning to the ice for some Summer skating training, the injury was still present and nagging his workouts.
The surgery is thought to be a success and his recovery time is in the 6-to-8 weeks range, which would put him back on the ice around the start of the regular season, likely missing out on a week, two or possibly three, depending on when he is able to get back on the ice. With the season two months away, everything is going to be very close.
You may want to take this into account, when you're eventually doing your projections for the season.