As great as Santana has been this year, I would not want to sign him to a lucrative long-term deal.
He has been so up-and-down throughout his career, I'd be nervous to do something like that. Those are the types of guys that can hamstring a small-market like Kansas City for YEARS if they go bad.
As far as trade pieces...
Here are guys who could be "headliners" in a big deal:
1) Kyle Zimmer. Doesn't profile as a true ace (Verlander/Kershaw/King Felix), but then only a few minor league guys have that type of upside. Profiles just fine as someone with James Shields/Zack Greinke level potential. Highly unlikely to be traded for anything but a young player controlled for multiple years with star potential.
2) Yordano Ventura. Stuff and results are great, and his durability has been just fine. Electric arm. Could be moved, but the Royals love him.
3) Miguel Almonte. Recent reports have placed this guy on the same level as Zimmer as a prospect. Very similar to Julio Teheran in terms of stuff and potential. More moveable, I think.
4) Adalberto Mondesi. He's so far away, his trade value isn't as high as it should be. Still, a 17 year old playing full season ball and slugging .150 points higher than his BA (current totals) while also playing defense that will stick and be above average at SS? Yes, please. Least likely player to get moved.
5) Bubba Starling. Crazy upside is still there, and he's starting to hit now at Lexington. Only question is hit tool. Everything else is easy plus.
6) Orlando Calixte. Middle infielder with big power potential. Not sure he can stick at SS, but he hasn't proven he can't. Early returns at Northwest Arkansas have been mixed with the bat. Doesn't have the same value as the other 4, who are all top 50 types.
7) Jorge Bonifacio. Big-time hit tools and power potential aplenty, he's performing well in a tough hitter's environment (Wilmington). Less positional value but better bat than Calixte.
There are a host of guys that can be added/subtracted to get to a deal for a more major piece:
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