OF Harrison Bader
One stated interest of John Mozeliak this deadline is a right-handed hitter who can play some center field. Harrison Bader has primarily been a center fielder, but he may still be an interesting trade acquisition. He recently turned 30, and he's had a rebound year with the New York Mets.
Bader is slashing .262.308/.374 this year for a wRC+ of 97. He has 4 home runs and 9 stolen bases to go with a league-average hitting profile. That's already an improvement upon Dylan Carlson and Michael Siani, the Cardinals' current center field options who have wRC+ scores of 35 and 55, respectively.
Bader wouldn't be a step back defensively with the Cardinals; he's very familiar with Busch Stadium after having played there for 5.5 years. Bader has racked up 5 Outs Above Average and 2 Defensive Runs Saved this year. He would provide great defense in center with an improved offensive profile for the Cardinals.
Bader is making $10 million this year, so the Cardinals would be on the hook for a little less than half of that should they acquire him. It's not a lot of money, but it will require some finagling to finalize a fair deal. The Mets could ask for one of the Cardinals' #15-20-ranked prospects in exchange depending on financial compensation on their end. Seeing Harrison Bader roam the friendly confines of Busch Stadium one more time would be remarkable, and his personality would add to an already revamped clubhouse.