I am on the side of the aisle that believes this version of the St Louis Cardinals should be sellers at the deadline, if not before. To me the top two pieces that should be dealt are Lance Lynn and Seung-hwan Oh. This post is going to be an exploration of Lance's trade value.
Lance Lynn has been a very consistent pitcher for the Cardinals for 6 seasons. His ERA has always been consistent around 3.5 (career 3.36). His strikeout rates have been solid. He is an inning eater. To me, he is the prototype 2/3 starter. I would imagine that most playoff bound teams would love to have this guy in their rotation.
To determine his trade value, I am going to review the past 3 trade deadlines and try to determine the most comparable deal in each season. Thus, I am looking for a free agent to be 2/3 starter dealt in 2014, 2015, and 2016.
2014: John Lackey to the Cards is probably the closest comparable, but he was not actually a free agent to be. So, it is an imperfect match. Still, that is the best option.
THE DEAL: John Lackey and Corey Littrell to the Cards for Allen Craig and Joe Kelly
Allen Craig was, at the time of the deal, slashing 237, 291, 346. The Red Sox were obviously trading for track record. Although it never materialized, I think this can be considered a player that was believed to be a decent major league outfielder/hitter at the time of the trade.
Joe Kelly was a swingman with a solid 2 year big league career and a decent ceiling.
So, in short, the package was a pair of solid ML performers for the 2/3 type starter. Again, it is not a perfect comparable.
2015: Ironically, Mike Leake is the featured deal here. He was a 2/3 type starter and a free agent to be. He netted the Reds a pair of prospects.
THE DEAL: Mike Leake to the Giants for Adam Duvall and Keury Mella
Adam Duvall was not the prospect compared to the player he is becoming. On John Sickels' website, he was rated the 20th best prospect that season for the Giants. He was an older prospect also. He seemed a player like a Matt Carpenter (the prospect, not the player).
Mella was the 3rd rated prospect on the same site. Some reports (MLBPipeline) even believed him to be the top prospect in that system at the time of the trade. Granted, it was probably a bottom third farm at the time.
In short and retrospect, this trade is interesting as a comparable and in the fashion that it has developed. Mella remains in the Reds' system as the 17th best guy according to Sickels. Duvall looks to be a bit of a steal.
2016: While I think Lance Lynn is a better pitcher than Wade Miley and Miley had an extra year of control, his trade is probably the closest that 2016 produced.
THE DEAL: Wade Miley to the Orioles for LHP Ariel Miranda
Miranda seems to be, essentially, a LH equivalent of Joe Kelly at the time of that trade. He has been mostly a starter, but has had a sprinkling of bullpen work as well. He has actually been better since the trade than he was prior. However, Miranda appears to be a legit big league pitcher swapped for a 3/4 starter in Miley.
All said, I don't think any of the above suggests the return for Lance Lynn would be a plethora of star prospects. That being said, the Cardinals could be looking at an organizational top 5 prospect and a sweetener (organizational top 25).
Looking at a few teams that I would imagine will be needing starters at the deadline, let's review what the Rockies, Astros, and Indians would have to offer using that framework (a la the Leake to Giants trade). I will also take into account the Cardinals organizational needs (LHP, Infielders).
Astros: Theirs is still a pretty deep system. It is also a system similar in strengths to the Cards. They have a bunch of outfielders and RHP. LHP Framber Valdez and 3B Colin Moran would be a nice return. Moran has had a tough time matching his draft pedigree. He appears somewhat blocked in the near term and potentially long term in Houston.
Rockies: They match up very well with the Cardinals. The Rockies have a handful of solid LHP prospects and some decent 3B prospects as well. LHP Ben Bowden and 3B Colton Welker. This would be a bit more optimistic in terms of return. Other options are Tyler Nevin, Sam Howard, Ryan McMahon, and Harrison Musgrave. This should be Mo's first call.
Indians: In my opinion, this is probably the weakest of these three systems at this point following the Andrew Miller trade. Still, they could dig up some good options to make another real run at that elusive title. LHP Shawn Morimando and IF Erik Gonzalez.