1. Starting pitching
2. Bullpen help
This is clear to anyone who has watched the Cardinals this year. They need starting pitching help, and they need to revamp their bullpen.
The Cardinals seem intent on bringing in at least three starters this offseason. If they succeed in doing so, they'll have those three additions and Miles Mikolas in their top rotation spots, and then Zack Thompson and Steven Matz can duke it out for the fifth starter role.
My guess is the Cardinals address their rotation needs mostly through free agency, but they may decide to fill one of those spots through a trade as well. They could decide to trade some of their very valuable position players to acquire a front-line starter, or they could trade some of their overflow assets to bring in a back-end of the rotation guy.
For the bullpen, it'll be interesting to see how they choose to address that need. They could hand out a few small free-agent deals, use the overflow of position players to bring in some arms, hand out a large deal, or a combination of these things.
Outside of pitching, the only two needs that could be looked at would be center field or catcher. The Cardinals still seem very unsure about who their 2024 center fielder is, and there are rumblings that their catcher position may be in flux again.