OF Kevin Pillar
Kevin Pillar fits the rumored right-handed outfielder who can play some center field if needed as well. He's a veteran of the game, as he just hit his 10-year service time mark, and he's been strong defensively. Pillar has also seen an offensive resurgence this year since joining the Los Angeles Angels.
Pillar was a non-factor with the Chicago White Sox to start the season, but he's now slashing .288/.340/.488 for an OPS+ of 127 with the Angels in 45 games (150 plate appearances). He's only striking out 18.1% of the time, but his walk rate of 5.5% is paltry. Pillar has been a regular for the Angels, but he would likely be relegated to a bench role with the Cardinals, especially given their already crowded outfield.
Defensively, Pillar has taken a step back this year compared to previous years where he was well above average according to outs above average. Pillar has been a negative defender (-2) according to outs above average since joining the A's. He sits at -1 on the year. Defensive runs saved isn't very optimistic on his defense either, as he grades out at -4 there.
Pillar is a free agent at the end of the year, he's 35, and his performance in Los Angeles could be a facade. Luckily, he won't have to play every day in St. Louis. He still has ample speed (84th percentile sprint speed), and he's serviceable across the outfield. Even if his OPS drops to the .700 range, he still provides plenty of value off the bench for St. Louis. He won't cost much in return, and he would provide exactly what the Cardinals are looking for.
The issue is that acquiring Kevin Pillar isn't a sexy trade by any means. Perhaps he could be paired with another player on the Angels...