If Bader can hit at career levels, then he’s playable every day thanks to his defense and to a lesser extent his speed on the bases. If he hits like he did in any season other than 2018, then he’s probably a platoon guy/defensive replacement in center. Thanks to Bader’s elite defense, the Cardinals will likely let him play his way out of the lineup. That’s a wise approach, and whatever path Bader takes in 2020 — glove-first regular or glove-first bench piece — will help determine that outfield division of labor for the bulk of the season. 
Coming into the offseason, it was apparent that the Cardinals, reigning NL Central champs, had to address their outfield bottleneck. 
In recent days, the Cardinals have eased the pressure a bit with a pair of trades. First, they sent Garcia to the Rangers in exchange for cash considerations, and then they shipped Martinez and Arozarena off to Tampa Bay for highly regarded pitching prospect Matthew Liberatore, low-minors catching prospect Edgardo Rodriguez and a swap of competitive balance round draft picks. So the clot is smaller, but it’s still there. 
Edman has speed and positional flexibility — he played five different positions last season and thrived at most of them — and he showed something with the bat after his promotion to St. Louis. Offensively, there’s a real chance he regresses across a larger sample, but he does so many things well that he can still be valuable even at lesser levels of plate production. The guess here is that the Cardinals still leverage Edman’s ability to play a majority of positions while mostly leaning on him as the third baseman of first resort. Matt Carpenter is still on the roster (and signed through 2021), but the 34-year-old Cardinal stalwart showed signs of deep decline in 2019, particularly in the vital area of quality of contact. If, however, Carpenter shows signs of a resurgence in spring, then he may lay claim to that third base job. By extension, Edman would have to find his playing time elsewhere, and that would put him more in the outfield mix than he already is. That would mean he likely eats into O’Neill’s potential ABs. 
Unfortunately, teams these days don’t often proceed from notions of merit when making such decisions. If the Cardinals dispatch him to Triple-A for just a couple of weeks or so, then they’ll prevent him from earning a full year of major-league service time in 2020. That, in turn, would delay his eventual free agency by a full year. The perverse incentives are obvious, and given the outfield depth in place the Cardinals have more than enough cover to make such a decision and pretend it’s the obvious one.  Bader is a standout defensive center fielder, and the 25-year-old figures to remain as much for some time. The problem is his bat. For his career, he owns an OPS+ of 90, which isn’t unacceptable for a slick defender at an up-the-middle position. Last season, however, Bader slipped to a line of .205/.314/.366. He did show more restraint at the plate in 2019 in the form of a higher walk rate and a lower swing rate, but once again he was eaten alive by sliders from same-handed pitching. On top of all that, Bader’s average exit velocity of 86.6 mph, while a career high, was still in just the 16th percentile of MLB

1. Is a Marcell Ozuna reunion in the offing?

The 21-year-old Carlson has established himself as one of the top position prospects in all of baseball. For his career, he owns a line of .260/.350/.431 across parts of four minor-league seasons, and last year he authored an OPS of .914 at the Double- and Triple-A levels with 26 home runs, 28 doubles, and 20 stolen bases in 126 games. That production at the highest rungs plus his impressive scouting profile mean the switch-hitter and former first-rounder is ready for the majors. 

2. Will the Cardinals trade Fowler?

Ozuna was a steady source of home run power for the Cardinals over the last two seasons, but he fell well short of the heights he reached in 2017, his final campaign before the Marlins traded him to St. Louis. A 107 OPS+ from a defensively inconsistent left fielder isn’t optimal, but it’s certainly playable. Given that the Cardinals in 2019 ranked just 12th in the NL in home runs with Ozuna’s 29 and given Ozuna’s clubhouse popularity, the potential for a reunion is quite possible. This feels like the kind of thing that would need to be on the team’s terms, since there doesn’t appear to be a thriving market for Ozuna (the Reds are a distinct possibility, but that may be about it). If it does come to pass, it will be because the Cardinals fear the potential power drain and because they still have that 2017 upside to tantalize them (Ozuna just recently turned 29). Obviously, though, an Ozuna signing would thicken that still thick outfield situation.
He made his way to St. Louis via the Marco trade with Seattle in July of 2017, and he’s been on the outfield radar ever since. He’s fast and a defensive asset at the corners, and he’s also shown pop across 121 games at the big-league level. The pop is legit, and O’Neill has 30-homer potential if allowed to play every day. Playing every day, though, has been an elusive goal for the 24-year-old. He’s been back and forth between the majors and minors, and he’s landed on the IL four times in two seasons. That said, O’Neill remains a tantalizing mix of power and speed, and the Cardinals badly need to see if he can find his level in the majors on a sustained basis. Doing that requires consistent playing time. Shildt understands this notion, especially in comparison to his predecessor in the St. Louis dugout, and Kolten Wong among others would surely vouch for this. Again, this crowded mix is working against O’Neill. 

3. Will they manipulate Carlson’s service time?

He’s still enough to dream on that O’Neill could be part of a trade for a more established piece. While O’Neill isn’t enough of a draw to be the center of an Arenado package, he could be involved on a “sweetener” level. That circles back to the possibility that an Arenado trade could provide further outfield clarity. Here’s where we should again note that such a trade probably won’t come to pass. That circles us back to the need for the Cardinals to find regular duty for O’Neill. And what if the Cardinals manage to swing a trade for Nolan Arenado of the Rockies? Such a turn of events seems unlikely, but there have been well sourced rumors to that end. An Arenado blockbuster might involve one of more of these outfield names, so rather than pressing Edman fully back into the outfield fray, it might actual thin things out. 
As for the path forward, what seems likely barring further changes is that Fowler would mostly pin down right, with Bader in center, and O’Neill in left, with Edman as a floater and Thomas as depth. “Barring further changes,” though, is the key qualifier, and it’s entirely possible that the current arrangement gets whittled down further between now and Opening Day. What those changes might be will, likely in full measure, be determined by how the following seven questions are answered by Cardinal decision-makers. 

4. Can Bader hit?

After a disastrous 2018, Fowler bounced back to adequacy last season. “Adequacy,” though, is the operative. He soon turns 34, and he hasn’t been both healthy and highly productive on the Cardinals’ watch. He’s also got two years and million left on his contract. While Fowler is a favorite of manager Mike Shildt and still has his uses, the Cardinals can likely improve their lot by replacing Fowler as the primary in right. That would probably require a trade.  
Our own R.J. Anderson recently reported that the Cardinals are willing to eat at least some of the money that Fowler is owed in order to move him. Such a move would make a lot of sense for St. Louis from the roster flow standpoint, and might clear the decks for Carlson. Speaking of which …

5. Will Edman have a path to playing time at third base? 

Back were Dexter Fowler, Harrison Bader and super-sub Tommy Edman, who merits regular playing time somewhere. Also back was Tyler O’Neill, who badly needs consistent reps at the highest level in order to determine what kind of present and future he has. Jose Martinez, defensively stretched to the point of breaking at really any position, was also still in the fold. Tooled-up Randy Arozarena was pressing for playing time, and top prospect Dylan Carlson had proved ready for a promotion. Also in the mix were Lane Thomas, Justin Williams and Adolis Garcia. To bellow the obvious, those are a lot of names for three spots plus bench detail. 
There are worse problems to have. The Dodgers, for instance, have in recent years dealt with a surfeit of outfielders, and they’ve benefited from the roster depth. Also bear in mind that starting in 2020 active rosters will expand 25 spots to 26, and that eases the pressure a bit. On another level, having a deep mix of handedness on the bench may be more valuable than ever now that relievers must face at least three batters (or end the half inning in question). Those new wrinkles both make the St. Louis outfield situation a bit less desperate, if that’s the word for it. 

6. Do the Cardinals see O’Neill as a potential regular? 

Now comes the part where we lay out those questions. 
Even so, Carlson figures to be able to help the Cardinals from the outset, if allowed to do so. While he’s eventually probably going to wind up in a corner, for the time being he can play all three outfield spots. As well, Carlson at the plate is better from the left side, and the Cardinals could use some additional pop against right-handed pitching. If Ozuna isn’t re-signed and Fowler is dealt, then perhaps Carlson will crack the Opening Day roster. 

7. The best guess

So how does this get further sorted out? Let’s make a guess that is at best vaguely informed. Let’s say the Cardinals cut bait on Fowler by trading him away along with a bunch of cash in exchange for a thoroughly forgettable prospect or two. Edman emerges as the primary third baseman in camp, and Carlson makes the Opening Day roster. Speaking of Opening Day, the Cardinals on March 26 in Cincinnati start Bader in center, Carlson in right, and O’Neill in left. Ozuna, meantime, is in left for the Reds. Thomas and Williams — both already on the 40-man — make the Cardinals’ active roster as reserves. That’s a plus defensive outfield at every position with significant offensive upside at the corners. There’s also depth on the bench. 
Whether things will unfold in such a way is the heart of the matter for the Cardinals at the moment.