Heading into the season, the St. Louis Cardinals were viewed as a team with an aging core. Matt Holliday, Yadier Molina, Adam Wainwright, and Jhonny Peralta are all comfortably into their 30s. The youngest player with a long-term contract, Matt Carpenter, will turn 30 this offseason. The only other player the Cardinals have in the mid-to-late-20s making a major contribution this season is Lance Lynn. While the Cardinals have benefited from continued production from their group of aging players, for the Cardinals to succeed this season and beyond, they were going to a need a new wave of players to contribute. A host of players have combined to give the Cardinals the most productive 25-and-under group in all of Major League Baseball.

In the winter, the Cardinals brought in Jason Heyward as a potential core player and in February, John Mozeliak discussed with Derrick Goold about the need to identify another core player this season.

"When you look at our model, it is making sure that you always have that core player or two that you're building around. As our current core grows older, someone else has to step up. That may look like Matt Carpenter. It may look like Kolten Wong. It may look like Heyward. Who knows? That certainly has been one of the reasons we're successful because we've had those middle-of-the-order-type hitters that we've been able to build around. And we augment that with our minor leagues."

While the Cardinals have yet to lock up Jason Heyward as the next core player, he has certainly played like one, hitting .293/.350/.445 for a wRC+ of 119 on the year. Between steals and baserunning, he is ranked seventh in all of baseball for baserunning, per BsR at FanGraphs. Those numbers put Jason Heyward comfortably in the top quarter of offensive players in baseball without even considering his defense. Add in his defense, and he is one of the best players in Major League Baseball. Factor in his youth and Heyward screams core player. Heyward has exceeded 4.0 WAR in each of the past two seasons. The only player in baseball younger than Heyward to accomplish the same is Mike Trout.

Heyward is not the only 25 and under player to perform well among position players. The Cardinals have received contributions from Kolten Wong, Randal Grichuk, and Stephen Piscotty as well.

Name PA AVG OBP SLG wRC+ WAR Jason Heyward 493 0.293 0.350 0.445 119 4.1 Randal Grichuk 312 0.284 0.333 0.561 142 2.9 Kolten Wong 525 0.261 0.320 0.390 97 1.9 Stephen Piscotty 145 0.336 0.372 0.552 152 1.4

Combined, the above players account for more than half of the team's position-player WAR. When comparing the contributions the Cardinals have received from young players, they match up very well with the rest of MLB. The graph below shows position-player WAR from players 25 years old and younger this season.

The Cubs top four of Anthony Rizzo, who is barely older than Heyward, Kris Bryant, Addison Russell, and Kyle Schwarber have made positive contributions for the Cubs while the Red Sox have gotten very good production from Xander Bogaerts, Mookie Betts, and of late, Jackie Bradley, Jr. The Cubs have roughly twice as many plate appearances as the Cardinals group as Jorge Soler and Starlin Castro has struggled. The Cardinals offense has been criticized for much of the season, but it is the young group of players that have provided the necessary punch along with Jhonny Peralta and Matt Carpenter. For players 25 years old and under, the Cardinals are actually ahead of the Cubs and lead all of MLB with 44 runs above average. The debate about Grichuk's sustainability and what Piscotty's line will look like once he comes down to earth a bit will continue on, but the Cardinals hitting production is only half of the equation when it comes to production from young players.

The Cardinals have also gotten great production from Michael Wacha, Carlos Martinez, Trevor Rosenthal, and Kevin Siegrist. In all of baseball this season, there are only 17 pitchers Age-25 and younger with an fWAR of 2.0, and the Cardinals have three of those pitchers. No other team has more than one such player. Here are the main 25 and under contributors for the Cardinals this season:

Name IP ERA FIP xFIP WAR Michael Wacha 157.1 2.69 3.25 3.67 3.2 Carlos Martinez 154.2 2.91 3.30 3.27 2.7 Trevor Rosenthal 60.1 1.49 2.15 3.30 2.1 Kevin Siegrist 60.2 2.23 2.88 3.71 1.2

With the hitters above, the Cardinals were in a grouping among several good teams at the top. There is no such grouping among the pitchers.

Only three teams have even half the fWAR that the Cardinals young pitchers have accumulated this season. Take the two together, and we can get an even better idea just how impressive the Cardinals' young players have been this season.

The Cardinals total is 40% above the second-place Cubs and is double that of more than two-thirds of the teams in baseball. The Cardinals have gotten fantastic contributions from an emerging core of players that can complement the team's existing base. The young core is one of the most productive in history. This season, the two groups have combined for a great run of success and potentially the first 100-win season in MLB since 2009 when the New York Yankees won 103 games on their way to a World Series title (Edit: The 2011 Phillies were the last team to win 100 games. Thanks to @alexcards79 for pointing out my error). While Kolten Wong has struggled of late, he has been an above-average player all season long and the Cardinals have him under control for four more years after this one. They will have Grichuk for five more seasons and Piscotty for six years after this one. Wacha, Martinez, and Siegrist are controlled for four more years as well with Rosenthal for three more years. The only player the Cardinals do not yet have under team control for beyond this season listed above is also the best player on the list above: Jason Heyward.