Eduardo Rodriguez
I saved the least flashy starter for last, Eduardo Rodriguez would be an instant upgrade to the Cardinals' rotation and will surely be traded at this year's deadline.
In 8 starts this year, Rodriguez has posted a 1.57 ERA in 51.2 innings pitched. He's bounced back from two rough seasons in a row and will be pitching for another long-term contract all season.
Rodriguez has 3 years, $49 million left on his deal but has an opt-out after this season. If he continues his current performance, he could opt out and secure an even larger deal.
The Tigers won't hesitate to capitalize on his value right now if the Cardinals come calling. While there should be some regression coming from Rodriguez, he still represents a great stabilizing piece for the Cardinals rotation this year if they really want to try and win this division and see what happens in October.