I do believe the leadership group is fragile and that resonates down to the rest of the team.
Going back to 2014-15, the time where the initial part of the "core group" formed (Monahan, Gaudreau, Backlund, Giordano and Brodie), anytime there's been expectations placed on them they fold.
14-15, the comeback kids the magical run to the 2nd round, there was no expectations that year, no pressure, sure it was unsustainable and lucky but it feels like they were just loose and having fun since they had no "pressure" on them.
15-16, they enter the season coming off a 2nd round playoff appearance, just acquired a young top 4 defender in Dougie Hamilton, expectations of making the playoffs but just an abysmal performance all year, the only positive taken from that year was drafting Tkachuk.
16-17, enter the season with a new coach and goaltending tandem and no expectations really, just hoping the team would be in the race and possibly snag a playoff spot, which they did, however that was mostly due to the 13-1-1 run from mid Feb to mid March, then got swept by a Ducks team that was missing some key defenders (Fowler, and Lindholm or Manson, if I'm not mistaken)
17-18, trade 3 draft picks for Hamonic, bring in a veteran goalie, there were expectations placed on the group to better their performance from the previous year, talk of them getting to the 100 point mark as a team, an inconsistent season that had them sitting in 2nd place in the division when they bye-week came about then the train came off the rails and the season ended horribly, didn't even have our lottery pick because the trade.
18-19, enter again with a new coach and lots of new additions to the line-up (Lindholm, Neal, Ryan, Dube, Czarnik, Hanifin, Valimaki) the only expectations was to fight for a playoff spot and not fold as they did the previous season. The team goes on to have one of the franchise's best regular seasons, largely carried by the play in the 1st half, as their play dropped dramatically after the all-star break.
18-19 playoffs, entering as the top seed in the west, expectations of a deep run, most fans hoping for a push to at least the 3rd round, they get run out of the building by MacKinnon and lose in 5 games to the 17th ranked team in the NHL
19-20, expectations of making the playoffs in consecutive years for the first time since they made it back to back in 08 and 09. A wildly inconsistent season thus far, being shut-out 6 times, having the horrendous 6 game losing streak only to be propped back up into playoff contention with a 7 game and a 5 game winning streak, the Bill Peters' saga, the TJ Brodie incident, their inability to score goals going from 2nd last season to 25th so far.
In my opinion, I don't believe the "core" group and leaders on this team know how to handle/perform under pressure, I would hope Treliving is going after Gallant or Laviolette to coach this group but I'm not too optimistic about that. I would ride the rest of the season out maybe call-up some deserving AHL guys (Czarnik, Quine, Gawdin), I wouldn't trade any picks or prospects for a rental as I don't believe this team is close to competing for the cup yet. If you miss the playoffs or get embarrassed in the 1st round, then start to look at the "core" group and make changes as necessary (I'd keep, Lindholm, Tkachuk, Dube, Andersson, Valimaki and Rittich, the rest can be moved for the right price). Tre has 1 more coach hire to really right this ship.
My take here could be completely wrong, as the team could come out of the break looking absolutely world class and go on a run, but based on what we've seen to date, I don't think that would happen.
TLDR: I don't think the core group can handle/perform under pressure, give them the rest of the season and see what happens before making any rash decisions.