What if Matthews crosses the street and tears his ACL? A lot of what if's. But they still have time to see where the LTIR people are and maybe things change. There's depth and you can't expect long-term injuries to everyone.
Liljegren isn't playing and they obviously don't like his game very much. When healthy, that probably won't change and they could use the cap space/roster space regardless. If there's a trade to be made, they should make it. Or you know... play him.
Obviously if Matthews goes down that's a fairly irreplacable player. However, injuries in hockey will happen -- it's just a matter of when and to whom.
It would be a fairly safe assumption to assume that a defensive core of Rielly, Tanev, OEL, McCabe, Benoit, Timmins and Hakanpaa will always have at least 1 guy on the LTIR. They're fairly old.
Don't get me wrong, I'm not saying that they should keep Liljegren. I'm simply saying that they don't need to be rushing out the door to trade him either. If all they do is go out and get a 2nd or 3rd round pick for him, and the next night OEL suffers a fairly significant injury, they're going to be caught with their pants down for absolutely no reason.
Now, if you can get something of real value, that's obviously a different story, but even though Liljegren has clearly not endeared himself to Craig Berube, I think he probably holds more value to the Leafs than a guy like Calle Jarnkrok... so if all you're doing is getting a mid-round pick, might as well shed Jarnkrok when he's healthy enough to return.