#5 - One of Brendan Donovan or Nolan Gorman
Brendan Donovan and Nolan Gorman have found their names in trade rumors for quite some time now. Unlike O'Neill, their names are not in these rumors because the team wants to move on from them, instead, their names are floated around because of the potential value the Cardinals could get in return for him.
Other names we'll discuss could be a part of smaller moves the Cardinals would want to make, but if Donovan or Gorman were dealt this offseason, it would surely be a part of a package to bring in a high-caliber starting pitcher or a cost-controlled arm to add to their rotation. The Cardinals do not want on from either of these guys, so it's going to require them to get massive value in return to consider a move.
Gorman is a former top prospect in baseball who boasts incredible power from the second base position, and the Cardinals do not have another player like him in their system who they can replace him within their lineup. Left-handed power is extremely valuable in today's game, and it's a part of championship-winning ballclubs. That's why other teams are going to covet Gorman in trade talks, and the Cardinals will have to weigh whether it's worth giving him up for starting pitching or not.
The same can be said for Brendan Donovan for different reasons. Donovan is not someone you want to trade if you're trying to win a World Series. Donovan is a winning player and impacts the game in so many ways. He can play almost every defensive position, giving the Cardinals a Swiss army knife for every game. Oftentimes, these versatile defenders don't have very good bats, but Donovan is one of the better young bats in our game, posting a 124 wRC+ so far in his two big league seasons. Donovan is a left-handed bat who gets on base at an elite clip and is developing more power, and that's someone the Cardinals should want in their lineup.
I put them fifth on this list because even if they trade for another starting pitcher, I think they'll do so in a deal that avoids giving up one of these two. If they traded for a Glasnow, it surely wouldn't require either of them. If they traded for Cease, I think they can send a package that centers around their top prospects instead. Ultimately, I don't think they'll move either guy, but I also would not be shocked by it either.