Who is "probably" in?
Ryan Fernandez and one of Matthew Liberatore/Zack Thompson
This next group is guys who are expected to take two of the remaining three bullpen spots, one due to roster flexibility and the other due to bullpen construction.
Ryan Fernandez was taken by the Cardinals in the Rule 5 Draft from the Boston Red Sox organization, one of four relievers the Cardinals acquired this offseason with ties to Chaim Bloom. Fernandez uses the trendy fastball-slider combination to get outs from the bullpen and has seen great success with producing swing-and-miss from his slider. If Fernandez has a solid Spring and the Cardinals feel like he can contribute next year, he'll make the Opening Day roster since he would have to be returned to Boston if he did not.
Matthew Liberatore and Zack Thompson are both left-handed starting pitchers who have seen various opportunities in the Cardinals rotation and bullpen over the last few years. Thompson found more success than Liberatore in the rotation in 2023 and seems to be the "next man up" if an injury or subpar performance comes from their rotation. While the Cardinals do have other left-handed options they can go to out of the bullpen, I do think one of these two will likely open the year in the bullpen for St. Louis while the other begins in Memphis to stay stretched out as a starter.
I could see a world where both Liberatore and Thompson make the Opening Day roster, with one functioning more as a long-man and spot starter, while the other is a left-handed option in shorter stints. Gordon Graceffo, Michael McGreevy, Drew Rom, Sem Robberse, and even Tekoah Roby already give the Cardinals starting pitching depth if they want to utilize Thompson and Liberatore in other roles.
I wouldn't be shocked if Fernandez and one of Thompson or Liberatore don't make the bullpen for Opening Day, but I would be surprised if those moves didn't happen.