Yeah, they're 1 piece away from havign a really good D... it's a little different when that 1 piece is a #1 or #2 defenceman, or a really solid #6.
The vast majority of the teams in the league, if you added 1 stud defenceman to, wuld be instantly elevated to at or near the top of the league.
The list of guys that would put this defensive group "to the top", while being theoretically potentially available is probably pretty short. Parayko, a healthy Connor Murphy would be ideal targets. Rasmus Andersson too. Adam Larsson would have been an excellent addition as well.
The big question of course is -- do the Leafs have the pieces and flexibility to actually acquire one. On the surface, I think you could make an argument that the answer to that is yes. Liljegren & OEL gone makes for $6m of usable cap space, while they've got a few young expendable pieces.
The other challenge to consdier as well though... is age.
Detroit isn't trading Mo Seider, Boston's not trading Charlie McAvoy or Brandon Carlo. NYI's not trading Noah Dobson. The guy you're going to acquire is likely going to be 28-29 or older.
Rielly's 30, Tanev's 34, OEL's 33, McCabe's 30... this is become to be a fairly old group... especially if Liljegren is on the way out.