The Red Baron did some great work on his Top 21(ish) Cardinals prospects this year. Here are the players that project as second-basemen that were included on the list, including the "just missed" section (indicated by "JM"):
Aledmys Diaz (6)
Darrin Seferina (17)
Jacob Wilson (JM)
That's it. You could make a case for Edmundo Sosa, who the Baron ranked 3rd, but he also believes he will stick at shortstop, and there's also the fact that he's a less interesting prospect if he moves to second. Paul DeJong could end up there, but with better arm than range he's probably a better fit at third. Bryce Denton should be mentioned in the same sense as DeJong, as a possible second-basemen that is probably a better fit at third. Add in that he's not going to start the year in full season, and his high-K, power, risk and reward profile and he's certainly not someone to count on, if at least someone to continue to monitor. Allen Corboda could move there from shortstop, but without much pedigree or track record, and with how far away from the majors he is, counting on him in any significant manner wouldn't be wise.
Diaz is probably the most polished of these three players and the one most likely to contribute this year. I have to imagine Wong's extension, like the Gyorko trade, shows that the org is not making any bets on Diaz at this point in terms of a starting role. Diaz was signed to a four year deal but he still needs to reach six years of service time in order to become a free agent, so at this point he is controllable for longer than Wong even with the extension virtually as long as he doesn't make the team out of Spring Training and stick from there.
Darrin Seferina is likely to start the year at High-A as a 22 year old. Prior to the extension, Wong was controlled for four years, so presumably if Seferina was going to make it to the majors (and as a player who could make an impact) he would do it before Wong would have entered free agency. While Seferina's stats and the Baron's description of him as a "pure hitter" make him worth being aware of, nothing about him really should make John Mozeliak and company think "Nah, it's not worth giving Wong this money when this guy could replicate his production in a few years". Not that Seferina can't end up being an average big leaguer, just that it's nothing a team that competes year in and out should depend on at this point.
Jacob WIlson doesn't really factor into this discussion, as the only reason he made even the "Just missed" section is because of his proximity to the majors and the possibility to contribute in a very limited role in the short term. When looking at the Cardinals' long-term options as starting second basemen, Wilson just doesn't make the cut.
There's also of course new comer Jedd Gyorko. Gyorko isn't exactly Wong lite, though. Both players were called up to the majors in 2013, but Gyorko is two years older, and in 300 more career PA has been almost a win worse. I like the Gyorko trade, because it finally got the team a decent backup infielder, but let's not pretend that he wouldn't be a downgrade compared to Wong going forward.
So, behind Kolten Wong, the Cardinals organization isn't exactly overflowing with talent at the keystone. Four years is a long time, but there's really only one option in the minors that right now looks like they could end up being as good as Wong and that's a guy who just finished his first full-season league last year and hasn't made any Top 10 lists for a team with a (somewhere in the vicinity of) average farm system. In that context it's actually pretty easy to see why Wong was extended. The Cardinals like to think several years in advance and while 2020 and 2021 are still pretty far away, it just became a lot more likely that second-base is filled by at least an average to above average player.
There's also the Cardinals' infield picture as a whole. The team will have to find someone else to man shortstop when Peralta's contract runs out in two years. While I am a huge supporter of Jhonny truly being a good shortstop, in two years this probably won't be true, so extending Peralta doesn't solve the shortstop problem.
At the same time, Matt Adams had a horrific 2015 before once again succumbing to injuries, and he's the only real first basemen signed passed 2016. Many here at VEB have been hip to the idea that Matt Carpenter could eventually move to first, and that's a future that I think makes a lot of sense. But that just moves the problem to third. Stephen Piscotty has had some time at first too and will probably see some more time there this year (hopefully when a lefty is on the mound at least) but with the defense Piscotty has shown in the corner outfield means he's certainly more valuable long term in the outfield, where things start to get thin as soon as next year anyway. Essentially, Matt Adams represents a risk that could create a hole at either first or third.
The Cardinals' long term 3B, SS, 2B options aren't bleak, but they're not so strong that they shouldn't be looking for extra years of control of a solid second-baseman at a decent rate. Edmundo Sosa and Paul DeJong are the most intriguing options to me, and they're certainly not slam dunks. Seferina, Diaz, and Mercado are also players that have some chance of claiming a starting role on future Cardinals teams, but are at least a tier below Sosa and DeJong in my mind at least.
So the Cardinals have a shortstop to replace in two years, and a first basemen that hopefully won't need replacing for three more years but has a legitimate chance of being a hole as soon as 2017, with Piscotty back in the outfield, Moss gone, and possible Holliday gone too. Even if Adams ends up playing well the next three years, he reaches free agency after that anyways, and we are talking more about the long-term future here, the years the Cardinals' have gained in Wong's extension. And really, in Wong's option year, 2021, Matt Carpenter isn't even under team control. This extension made Wong the only infielder under contract in 2021 and indeed only Mike Leake is controllable by that year under a rarely exercised mutual option
This context also speaks volumes about the value of gaining two more years of Wong, even if it's just of the boringly average variety. Like the Leake signing, Wong's extension is about raising the floor of future Cardinals teams. While the Cardinals signed Leake despite pitching being the strength of the farm, the infield after the extension in no way projects to be a logjam over the short, medium, or long term.
Being that most of the Cardinals' position prospects of note reside in the middle and lower minors, there is a higher level of uncertainty involved. This uncertainty not only applies to second base but all around the infield, with Matt Carpenter really the only other infielder entrenched in the Cardinals org. Diaz, Seferina, DeJong, Sosa, Mercado, and Denton all have their value, but there's a much better chance that two of them turn into MLB regulars than three. And really, only one might end up being a significant contributor, if that. Controlling Wong for 2020 and 2021 gives the Cardinals a much better chance of fielding a quality infield at reasonable prices for years to come. Adding just one consensus top 100 prospect in there might change how easy of a decision this was, but that's not the case here.
You probably notice this has been entirely a qualitative analysis, rather than quantitative. In fact, to this point, I'm over 1,200 words in and I haven't even mentioned how much Kolten's getting guaranteed, which is $25.5M, with an option year for $11.5M more than the buy-out. Typically, my pieces are all about the numbers. For Wong's extension, this would probably involve comping his contract to the prices second basemen like Wong have received in arbitration, adjust for inflation, and so forth to get an idea of what the Cardinals are really paying for his free agent year and for the privilege of having an option on the second free agent year.
That practice would be most important for the team themselves. The Cardinals undoubtedly use something to project arbitration prices for every type of player, and they undoubtedly have a model for how they expect a player like Wong to progress. This allows them to find very accurate prices for what they'd be willing to guarantee for a player like Wong through arb and their first few years of free agency. This process would allow them to save a few million dollars, which is undoubtedly important to the investors and those paid who are paid by them, but less important for budgetary flexibility.
What I'm getting at is that Wong's extension, at $25.5M spread out over five long seasons, doesn't really handicap the team's finances in any real way, and what the Cardinals end up paying Wong during his arbitration years certainly isn't going to be more than a million or two off the average price that you could expect the Cardinals to pay Wong. Much more important is that with inflation, if Wong simply has a 2 WAR season in 2020, the contract is mostly paid for in that one year, even if he was replacement level over the first four.
His $10.25M salary in 2020 only buys about one and a quarter wins now, it might not even buy a single win in 2020. Because of that, it's very hard to see this deal going south except when Wong takes the Allen Craig career arc, which is probably a pretty unlikely outcome. Even so, the total doesn't even match the amount the Cardinals agreed to pay Jaime Garcia this season, less when considering inflation. It's certainly apples and oranges to compare the risk of a pitcher in the present to a position player in the future, but the point remains that $10.25M is certainly an amount the Cardinals are willing to make a smart gamble with.
So while we can quibble on whether the deal was a good one or not in terms of maximizing asset value or whatever, the important thing to me is: It's very easy to see the Cardinals having a shortage of infield talent in 2020 and 2021, he's always been a low ceiling but high floor player, he's had two years of around average production already, average players are expensive in free agency. All that adds up to me that getting Wong under cheap (and with the option, flexible) terms for additional years is a very easy call. Now let's see if they can do the same with El Gallo.