Nimmo had an OPS of .995 after returning. He's playing somewhere. The question is whether you are confident enough in Smith and/or Davis to trade Conforto for a centerfielder plus something, whether you think Smith or Davis can get you the centerfielder you need, or whether you think the offense you have is worth the defensive risk. Betts isn't really a centerfielder. I'm not sure our farm system is where it needs to be to make Betts an option for 2020 anyway. The fielding bible has Marte at -9 runs saved in center on the year. Nimmo was a -2 in about a quarter of the innings. And Marte has less offensive upside going forward. Basically he's what we've already got, only less. Pillar used to be an elite defensive centerfielder, but he's been average the last two seasons. Bradley is not as good defensively (past or present) as Pillar. Margot can field the position (+6 runs saved in 900 innings), and might be had cheaply, but he's basically Lagares from a few years ago with a slightly worse glove but a slightly better bat. If you think the offense you have is worth the defensive risk, he might be a useful add for support. One guy that wasn't mentioned was Harrison Bader. He had an overly high BABIP in 2018, and a criminally low BABIP this past season. An intermediate BABIP would put him in the same offensive category as Pillar or Bradley, and better than Margot, while being the superior fielder presently to all three (+13 runs saved in 900 innings last year). The Cardinals played Dexter Fowler ahead of him against righties in the playoffs, which tells me they are undervaluing him. That's where I'd kick the tires first.