They come. They don't go.
Theo Epstein said he wanted to build a "player development machine'' when the Cubs hired him in 2011, and he's done exactly that. So many impactful position players have arrived in the last two years that you might feel you can't even catch them.
So we did. We also ranked them in the order of their potential career WAR (based on career WAR to date, adjusted per 150 games played). Then we looked ahead two more years and found seven more position players who could arrive at Wrigley Field within the next two years.
Consider this a young Cub clip-and-save tool for the upcoming trading period, when Epstein is expected to seek upgrades that could pay dividends in October.
SEVEN IN THE MAJORS
1. Kris Bryant
Age: 24.
Debut: April 17, 2015.
WAR/150: 6.0.
In a nutshell: Bryant's smile pretty much tells the whole story. He's everything you'd want in a ballplayer -- a disciplined, powerful hitter in an athletic body with a graceful nature that caused him to be nicknamed "Silk'' when he was a teenager. He moved all over the field at the University of San Diego and has continued his wanderings in the Major Leagues. He's been a defensive asset at third base (+3 Defensive Runs Saved, per Fangraphs) and in left field (+5 DRS).

2. Willson Contreras
   Age: 24.
   Debut: June 17, 2016.
   WAR/150: 5.6 (it was actually 11.25 before his home run on Wednesday but given the very small sample size we cut it in half, figuring every week won't be like his first week).
   In a nutshell: Contreras, a gift from Jim Hendry to Epstein, has been in the Cubs' system longer than any player on the roster. The Venezuelan catcher is the complete package -- strong armed behind the plate and the ability to hit for power and average (.338 with 17 home runs in 180 games between Double-A and Triple-A). He's a good bet to become the Cubs' primary catcher later this season and MLB Network Radio's Jim Bowden says he could be the second best catcher in the National League in 2017, behind only Buster Posey.

3. Addison Russell
   Age: 22.
   Debut: April 21, 2015.
   WAR/150: 3.4.
   In a nutshell: The Cubs raised their level of play when he moved from second base to shortstop last August. He's a low-floor player whose quick hands and textbook mechanics -- "no chrome,'' according to Joe Maddon -- make him the kind of player who could win the Gold Glove every season once he wins his first one. He has a lot of room to grow as a hitter, with the improvement coming when he gets more comfortable against left-handers, surprisingly (.156 career average in 109 at-bats against left-handers.

4. Javier Baez
   Age: 23.
   Debut: Aug. 5, 2014.
   WAR/150: 2.6 (Baez was such a raw product when he came to Chicago in 2014 that we calculated his WAR/150 using only 2015-16 totals; he'd be at 0.6 if you included his -1.0 WAR from '14).
   In a nutshell: Baez, a natural shortstop who has been blocked by Starlin Castro and Russell, has developed into a very valuable depth piece. He makes spectacular plays at third base while using his quick hands to get outs on tag plays, and has speed on the bases. Light-tower power was his calling card in the Minors, but he has cut down the length of his swing. Maddon has used Baez in 19 of the last 20 games, including 15 starts at third, short and second base. It may take a trade for him to have a position to call his own but he wants to be remain a Cub. Like Contreras, he predates the Epstein regime in Chicago.

5. Albert Almora Jr.
   Age: 22.
   Debut: June 7, 2016.
   WAR/150: 2.3 (like Contreras, he has played well within a small sample size, so we took his figure of 4.6 and cut it in half).
   In a nutshell: As smooth as it gets in the outfield, Almora is a plus fielder. He was Epstein's initial first-round pick (2012) for the Cubs after being a regular on Team USA, and appears very well prepared after playing 379 games in the Minor Leagues. The question is whether the bat will be dynamic enough for him to inherit Dexter Fowler's job on a permanent basis. Fowler is only under the Cubs' control through 2016 but is a strong candidate for a multi-year extension.

6. Kyle Schwarber
   Age: 23.
   Debut: June 16, 2015.
   WAR/150: 2.3.
   In a nutshell: It feels like Schwarber should be ranked much higher than this, but as a metric WAR generally rewards complete players (David Ortiz has averaged only 3.6 WAR in his 14 seasons with the Red Sox). He's as good of a hitter as Bryant -- the perfect left-handed complement -- and has homered once every 14.8 at-bats in the Major Leagues. Schwarber ruptured two ligaments in his left knee in a collision with Fowler in the second game of 2016. He's expected to make a complete recovery for 2017. He'll get his spot back in left field and will likely continue to work in order to be an option at catcher. He will make a deep, productive lineup deeper and more productive.

7. Jorge Soler
   Age: 24.
   Debut: Aug 27, 2014.
   WAR/150: 0.8.
   In a nutshell: The jury's out on the muscular Cuban, who signed a nine-year, $30-million deal in 2012. He was the most consistent hitter in Maddon's lineup during the 2015 postseason (.474 with 3 homers, 3 doubles and 6 walks in 25 plate appearances), but is batting .223 this season, and only .258 with a .745 OPS in 175 career games. Schwarber's injury opened left field for him this season, but he was in and out of the lineup before going on the disabled list with a strained hamstring. He's only touched on his potential, but is getting squeezed among the outfield options. The Cubs could benefit from him hitting well when he comes off the DL as he's a trade candidate.

SEVEN MORE WHO COULD BE CALLED UP IN THE NEXT TWO YEARS
1. SS Gleyber Torres
Age: 19.
Current level: High-A.
How he fits: Part of an $8.2 million international spending spree in 2013, Torres potentially could allow the Cubs to deal Russell or Baez for pitching after 2017. He's an all-around player with a cannon arm and ability to be a high-average hitter. Ben Zobrist is signed through 2019 but could be shifted back into his super-utility role to open up playing time at second base for Torres in a middle-infield role.
2. 3B Jeimer Candelario
Age: 22.
Current level: Triple-A.
How he fits: A switch hitter who can be productive from both sides of the plate, Candelario can expect to be promoted in September, if not before then. He had 22 doubles and 41 walks in his first 69 games this season. But with Bryant and Baez on the roster, he's little more than insurance, thus a potential trade piece.
3. 1B/DH Dan Vogelbach
Age: 23.
Current level: Triple-A.
How he fits: Chairman Tom Ricketts agreed to spend heavily in the last uncapped Draft, in 2011 -- a move that caught Epstein's eye and made him more open-minded about joining the Cubs. Vogelbach, a highly regarded hitter despite a soft frame, was the Cubs' second-round pick that year, behind Baez. He was hitting .302 with 12 homers and a .949 OPS in his first 65 games at Iowa this season. Unless the new CBA calls for the NL to add the DH rule, Vogelbach is blocked by Anthony Rizzo. He'll probably be up in September if not for a series at an AL park. He's an excellent candidate for a trade, especially to an American League team.
4. 2B/OF Ian Happ
Age: 21.
Current level: High-A.
How he fits: An advanced hitter at the University of Cincinnati, Happ was a first-round pick in 2015 from the same folks who landed Schwarber in '14 and Bryant in '13. He's pushing for a promotion to Double-A in his first full season as a pro. He's a switch hitter with power and speed, profiling as a potential 20/20 player. His fielding is behind his hitting, but he could be pushing for Major League consideration in a year.
5. OF Mark Zagunis
Age: 23.
Current level: Triple-A.
How he fits: A third-round pick in 2014 from Virginia Tech, the right-handed-hitting corner outfielder is an on-base machine ( .411 OBP in 236 Minor League games). With Jason Heyward set in right and Schwarber in left, Zagunis seems blocked but could challenge Soler and Matt Szczur for a role as a complement to those two left-handed hitters.
6. OF Eloy Jimenez
Age: 19.
Current level: Low-A.
How he fits: Jimenez was more highly regarded than Torres in the 2013 international class, but has had a slower adjustment to pro ball. He has huge power and a right-field arm. It's probably a stretch to see him in a Cubs uniform before 2019, but he's an intelligent, hard-working player who could start moving quickly. He seems more likely to be traded along the way than make one of his elders expendable.
7. OF Billy McKinney
Age: 21.
Current level: Double-A.
How he fits: A former first-round pick of the Athletics' acquired alongside Russell in the 2014 Jeff Samardzija trade, McKinney is a left-handed hitter whose development has stalled after he fouled a ball off his right knee last August, sustaining a hairline fracture in his kneecap. He's the rare Cub position-player prospect who is going the wrong way, but that could change quickly. He seems like a possible trade piece.
Also in the picture: OF John Andreoli, OF Jacob Hannemann, 3B Christian Villanueva, OF Eddy Martinez.