It's a hard trade to analyze because of the opt out.
It might a horrible trade. It might be fine.
My assumption was that Colorado might pay down some portion of Arenado's 2021 salary but the majority of the $51M would only become applicable if he does not opt out. But no! Morosi said:
Jon Morosi
@jonmorosi
Source: The #Rockies are paying Nolan Arenado's $35 million salary this season; $15 million is owed to the Cardinals in this calendar year, with the remaining $20 million deferred.
Which really makes it seem like the "$20 million deferred" is already locked in and guaranteed.
So in Scenario A where Arenado opts out, the Cardinals are giving up Gomber and the "prospects" and will have to pay Arenado $20M in 2021, but the Rockies at some point will reimburse them for the $20M. So it's like Gomber + the "prospects" for one year of Arenado that really only costs a couple million bucks, or whatever it costs to pay that $20M up front considering the time value of money blah blah. In Scenario A the Cardinals make out like absolute bandits because they get a 4 WAR player for not much more than Gomber and some s*** prospects. Arenado at a cost of say $2M is probably worth like $30M in surplus value and I doubt Gomber and Montero etc. combined are worth more than $10M.
Scenario B is where Arenado does not opt out. The Cardinals then pay him $214M through 2027, less the $51M from Colorado, so 7/$163M. He's 1.5 years younger than George Springer and projects to be slightly worse in 2021 by both Steamer and ZiPS....
.... Scenario B actually does strike me as a negative value scenario. I think Arenado has less than no projected surplus value on that contract and it has albatross risk. Gomber and the prospects aren't a big package to give up but they also make it a bit worse. People can say that he would absolutely get 7/$163 with the signing team sacrificing a high draft pick on the open market, and they might be right, but that doesn't make it a positive contract.
So the whole thing swings on whether or not he opts out. How do you straddle that risk? The negotiations must have been fascinating.
If he opts out after 2021 he will be opting out of 6/$179M. Pretty huge risk. Doubt he does that but he might if he has a career year. Is he capable of a 7+ WAR season?
If he opts out after 2022 it will be 5/$144. Again a huge risk. Again I doubt he opts out, but I think it's a but more likely for him to opt out after 2022 than after 2021.
The CBA will also be expiring before 2022 so that has to be considered somehow.
It's hilarious but St. Louis is likely hoping he is so amazing in 2021 and or 2022 that he just opts out and f***s off.