Cleveland Guardians
Typically, the Cleveland Guardians are known as a team that produces starting pitchers like crazy. That hasn't been the case this year, as they traded Cal Quantrill away this past offseason, and Shane Bieber is out for the year due to an elbow injury. Therefore, their starting staff has been toiling near the bottom of the league according to ERA all year.
In addition to starting pitching, the Guardians could also use a right fielder. Steven Kwan has been excellent in left field for them, but their right fielder, Will Brennan, has just a 92 OPS+ in right field, and his defense has been lackluster as well. The Guardians are likely prioritizing a starting pitcher to deepen a staff that needs some help, but they are likely also aiming to acquire a right fielder with plus offense and defense.
Luckily, the Cardinals boast ample outfielders who are strong offensively. Alec Burleson's emergence this year and Brendan Donovan's success in left field have once again created a log jam of sorts for the Cardinals. Tommy Edman is due back soon, Michael Siani has played some of the best defense in the league in center, and Lars Nootbaar remains a good all-around player in the outfield. Should Cleveland want to attempt a project, they could call about Dylan Carlson as well.
My focus is on Lars Nootbaar here. He holds quite a bit of trade value given his career wRC+ of 116 and the fact that he is hitting arbitration for the first time next year. In exchange, the Cardinals could target any one of Cleveland's more than capable relievers. Their bullpen has been the best in the league all year, so they are likely willing to trade from their depth to improve the outfield.
One reliever, perhaps Nick Sandlin, likely isn't enough to land Nootbaar alone. Therefore, the Cardinals could ask for a prospect in addition to Sandlin.