All the teams that I've seen Kevin Shattenkirk rumored to be traded to this summer.
NY Rangers, NY Islanders, Boston, Philadelphia, New Jersey, Detroit, Buffalo, Edmonton, Arizona and now Montreal.
These Shattenkirk rumors are getting ridiculous now.
Boston and New Jersey are probably the 2 teams that should be trying to land Shattenkirk due to the fact that they need the most help on defense out of all the teams listed above.
New Jersey may not have or want to give up assets to get Shattenkirk. Also not sure what St. Louis is looking for in return from New Jersey.
Boston does have the assets but I don't think they'd be willing to part with players such as Krejci or Pastrnak so that seems to be a sticking point for a St. Louis-Boston trade.
As far as a Montreal-St. Louis trade for Shattenkirk goes, I'm not sure if Montreal has the right pieces St.Louis is looking for other then Galchenyuk or Gallagher, and I can't see Montreal trading away their 22 year old projected #1 centre Alex Galchenyuk or their 24 year old #1 RW Brenden Gallagher for Kevin Shattenkirk.
If St.Louis decides to trade Shattenkirk they'd probably want a NHL ready forward a young defensive prospect and may also want a 1st round draft pick depending on what pieces are in the proposed trade for Shattenkirk.
Pretty good summary of why some Blues fans are a little worried about potentially losing Shattenkirk for nothing. However, it is highly doubtful the Blues want a D prospect coming back. They need forward prospects. We have two highly touted LHD propsects (Dunn and Walman) both with Top 4 upside, two young NHL ready LHD (Edmundson and Lindbohm), Parayko and Petro holding down the RH side long term, and Schmaltz being a Shattenkirk style RHD ready for duty this year or next. It would take a high-percentage top-pair LHD prospect to make us interested (Provo or Sanheim from Philly as an example).
Here is how I see the situation with all the teams you listed:
NJ - We'd want Zacha, maybe McLeod+. NJ is rebuilding and may not be willing to part with prime prospects. Zacha is being penciled into their lineup this year, maybe next so they'd possibly want a center coming back.
NYR - Doesn't have much Blues fans are interested in. Kreider+ or Nash. Kreider seems to be missing the toolbox to capitalize on his tools, and Nash is risky at that cap hit coming off of a poor season.
Boston - Krejci is too much value but coming off injury with a high cap hit is too scary to want to add much of value. Spooner is too little value and too similar to Lehtera in needing to be sheltered. This is the likely desperation landing spot. Either take Spooner+ because nothing else materializes or wait to see Krejci look healthy once the season starts and then add.
NYI - I'm not sure their interest level with Hamonic staying. They need forwards too, so not sure if they'd move them. But they do have pieces in Strome, Barzal and Nelson that could move the needle but doubt they want to part with the latter two. This isn't a landing spot that I have seen discussed much.
Philly - Something around Schenn could work, but Philly fans are adamant about rolling with their young LHD on the right side, so they don't see a need. I don't really blame them.
Detroit - Seems a good match need-wise. They have excess forwards to the point they will likely lose one via waivers and need D. Their GM, Holland, historically doesn't make big trades though. Heat has kind of died on this spot. Something around Tatar or Nyqvist, maybe a prospect or a pick added could work.
Buffalo - Need LHD, not RHD.
Edmonton - Shatty won't sign there. Agent told them straight out.
Arizona - Doubtful he'd resign there. They also have pretty strong D group for a rebuilding team. And I doubt a rebuilding team wants to move the young assets that are their best trade chips. Would probably want Hanzal+, and that isn't the most thrilling offer.
Montreal - Very little need, most likely Eklund wanting to get those rabid Montreal fanbase clicks. But oh Galchenyuk would be so nice between Tarasenko and Schwartz