Weren't too many differences between sides according to last week. Not terribly much to explain to mediators I'd think. Issue, as always, is who wants a deal and when.
There are two reasons to bring in mediators:
To try to pry the nhl off one of their four stances:
Economics, contract caps, variances and term
The other is an attempt to frame the nhl as not negotiating in good faith, which they clearly have been
If a deal is signed good, but mediation (in NHLPA case) is more a ploy for future shenanigans