Just heard on the Sportsnet Oilers Now podcast, since they also cover the Oil Kings some to extent, Bob Stauffer (host) said "I don't think Guenther is going to be able to play in the Memorial Cup based on what I saw when I saw him in the building the other night -- if he's able to come back from that, wow!"
Whatever that means. I don't know what the injury is but it sounds more than short term. Not saying it's long term (what TF do I know?) but it definitely doesn't sound like anything close to day to day.