Karlsson labors his way to just over 6 minutes in 3rd period of Game 4

San Jose Sharks star defenseman Erik Karlsson missed 29 games this season with a groin injury, and it doesn't require Sherlock Holmes' work to detect that he's been battling a lower-body ailment throughout the postseason.

However, Karlsson's injury appeared to take a turn for the worst during the Sharks' 2-1 loss to the St. Louis Blues in Game 4 on Friday night.

With San Jose on the man advantage midway through the third period, there were two instances in which Karlsson was noticeably laboring as he attempted to be first to a loose puck.

After the Blues cleared the zone, Karlsson had a gap on Ryan O'Reilly as he went back to retrieve the puck, but nearly lost the race and had to chop the disc out of harm's way. Later in the shift, Tyler Bozak received a scoring chance after chipping a puck past Brent Burns - a situation in which a healthy Karlsson almost certainly would've been able to cut him off.

Midway through the power play, the Sharks called a timeout. Karlsson left the ice and wouldn't return for over seven minutes until the final two minutes when San Jose's net was empty. Here's his ice-time breakdown, courtesy of ShiftChart:

It's no secret that Karlsson's effectiveness is directly tied with the Sharks' Stanley Cup aspirations. He won't have long to recover before Game 5, however, as it takes place Sunday in San Jose.