Liljegren has had some injury trouble in his young NHL career, but when he has been healthy, he hasn't been nearly as productive as what has been expected of him as a former 1st rounder (2017).
In terms of what his actual value might be, that's the million dollar question. Liljegren, being a right-shot defenseman, is certainly going to be an intriguing piece on the trade market. It's a reasonable expectation that the Leafs may want a player of a similar age and skill level in return, but until we receive additional information on that, it's probably best not to speculate too much.
For Liljegren, a change of scenery might be nice as well, especially if it means consistent playing time, which he does not appear in line for under Craig Berube in Toronto.