Ryan Helsley, Willson Contreras, and Nolan Arenado are traded, but Sonny Gray stays
Now for the painful part. The Cardinals are going to be trading some key players, guys that can help you win now.
Ryan Helsley makes the most sense to trade. He's got just one year left on his contract, is due for a significant raise in arbitration, and will likely be too expensive for the Cardinals to extend or re-sign next offseason. He'll bring back a good package too.
Willson Contreras came here to win and that hasn't happened, so I imagine he'll want a trade to a contender. The same can be said for Nolan Arenado. St. Louis does have some solid options at the catcher and third base positions that can take over for Arenado and Contreras, but I don't see either one wanting to sit through a rebuild.
Finally, there's Sonny Gray, who signed a three-year, $75 million contract last offseason and came here with the intent to win. He, Arenado, and Contreras all have no-trade clauses. Contrary to popular belief, I actually think Gray will use that clause to stay in St. Louis.
One of the reasons Gray signed in St. Louis is because of his desire to be close to his Nashville home. Being a Cardinal allows for that. He also just signed here last winter, so he may prefer not to be on the move again this offseason. John Denton even noted that Gray still wants to be a Cardinal.
Gray often raves about the Cardinals' young core and, similar to Adam Wainwright, has a very optimistic outlook. They need to have somebody who can lead the pitching staff and be a mentor for the younger arms. Gray remaining in St. Louis makes sense for both parties.
Steven Matz, Miles Mikolas, and Erick Fedde stay
I'll try and keep this one brief. But I just don't see anybody being interested in Steven Matz or Miles Mikolas. Matz has been unable to stay healthy and Mikolas has been ineffective over the last two years.
The Cardinals would have to eat the money for both embattled pitchers.
Erick Fedde was okay after being acquired by the Cardinals, but it just doesn't make sense to trade him. He's only making $7.5 million next year, and the Cardinals likely won't get anything good for him in a trade.