Sheldon Keefe releases concerning update on Auston Matthews.

The Toronto Maple Leafs are already in some pretty big trouble after giving up a 3-1 series lead to the Boston Bruins in their opening round Stanley Cup playoff series and, unfortunately for the Maple Leafs, things may be going from bad to worse.

On Sunday, head coach Sheldon Keefe shared some additional details on the sudden and mysterious departure of star forward Auston Matthews prior to the start of the third period in Game 4. After the game Keefe revealed that Matthews was dealing with some type of illness, but his comments on Sunday suggested that this illness may not be something Matthews can simply shake off.

"For whatever reason, it's not one of those run-of-the-mill everyday type of illnesses that sort of come and go," admitted Keefe on Sunday. "This one has lingered. The effects have lingered and gotten worse when he gets on the ice and is asserting himself.

That could be seen at times in Game 4 as Matthews was laboring late in the second period, so much so that some speculated that he has suffered an injury at the time. If that continues to be the case with Game 5 rapidly approaching, you have to wonder if Matthews will even be able to suit up with the Maple Leafs season on the line.