I think there is almost zero Paryenko is traded by the blues and they will match a offer sheet.

Unlikely I agree, but STL is only 5 below the cap (assuming flat) with 5 players including Paryenko to sign. They wouldn't be able to -without severe difficulty-match a 5 per offer let alone one for 7, so might be willing to listen to an offer. Toronto probably has to throw in another prospect, but definitely a non-zero chance it happens.

Personally I would protect Martin over Rychel and the Blues would trade others before Paryenko

I would give away a 2nd round pick plus a prospect to get rid of Martin, so wouldn't even consider protecting him.