4. Jack Flaherty
Teams will ooze at the youth and high ceiling of Jack Flaherty. Contrarily, volatility and a lack of team control hurt his value. On the season, Flaherty has a 4.27 ERA, 1.57 WHIP, 4.01 FIP, and is striking out nearly nine batters per nine innings. Flaherty struggled mightily with walks in his first few starts, but he seems to have that under control as of late.
Flaherty's true value lies in his ability to limit barrels and hard hits. His history of high strikeout rates and ridiculous WHIP numbers (0.968 in 2019) make him an interesting piece for any contender. He has a top-5 Cy Young placement on his resume as well.
Jack is a free agent at the end of this year, thus hurting his trade value. However, many teams would like to have his stuff as a third or fourth starter in a playoff rotation. Having the opportunity to negotiate and work on an extension before free agency may also be appealing to teams.