Since MLB.com started ranking rookies based on long-term value in 2015, we've had some strong debates for the No. 1 spot. Corey Seager vs. Alex Bregman (2016), Ronald Acuña Jr. vs. Juan Soto and Shohei Ohtani (2018) and Vladimir Guerrero Jr. vs. Fernando Tatis Jr. (2019) were extremely close calls with no obvious answer.

Which brings us to Julio Rodríguez vs. Adley Rutschman this time around. Rodríguez helped the Mariners end the longest playoff drought in the four major North American sports leagues (21 years) with a 25-25 season at age 21, while Rutschman led the Orioles back to respectability and staked an immediate claim to being baseball's best catcher.

Rodríguez is nearly three years younger than Rutschman and roaming the outfield comes with much less wear and tear than playing behind the plate. Would you rather have 15 potential years of superstardom or 10 at the most difficult position to fill?

Previous rankings: 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021

The age at which a player breaks into the Majors and becomes a star correlates heavily with his future value, so we're leaning toward Rodríguez. In our long-term rookie rankings below, we also note each player's seasonal age as of July 1, and it's no coincidence that three of our top five rookies played this year at age 21.
 
We also factor in present-year performance, past track record and future projection. Position players are less volatile than pitches, so we take that into consideration as well.
 
Our list considers only graduated rookies who have exceeded of 130 at-bats, 50 innings or 45 days of active service time in the big leagues. Orioles infielder Gunnar Henderson (No. 2 on MLB Pipeline's Top 100 Prospects list) and Diamondbacks outfielder Corbin Carroll (No. 3) are close to but not over the limits and thus not ranked.

1. Julio Rodríguez, OF, Mariners (age 21)
In addition to his outstanding tools and performance -- Rodríguez became the quickest player ever to reach 25 homers and 25 steals (125 games, three fewer than Mike Trout) -- he also has an 80 personality on the 20-80 scouting scale.

2. Adley Rutschman, C, Orioles (age 24)
The No. 1 overall pick in the 2019 Draft finished second to J.T. Realmuto in Wins Above Replacement (Baseball-Reference style) by a catcher this season (5.2) despite not debuting until late May because of a triceps injury.

3. Michael Harris II, OF, Braves (age 21)
The Braves tied the Royals for the most rookies on this list with three, led by Harris, who electrified the Braves with his bat and glove after making the jump from Double-A in late May. In the last 40 seasons, the only rookies age 21 or younger to top Harris' 5.3 bWAR are Trout (10.5 in 2012) and Rodríguez (6.0).

4. Bobby Witt Jr., SS/3B, Royals (age 22)
Witt entered the season as MLB Pipeline's No. 1 prospect, just ahead of Rutschman and Rodríguez. A potential five-tool shortstop, he became the fifth rookie ever -- and second-youngest behind Trout -- to post 20 homers and 30 steals.

5. Riley Greene, OF, Tigers (age 21)
The fifth straight 2019 draftee atop this list, Greene should emerge as very similar to Harris in the long run, albeit with a little less speed and defense.

6. Spencer Strider, RHP, Braves (age 23)
Strider went from winning five games and making 10 starts in three years at Clemson, where he had Tommy John surgery, to breaking Randy Johnson's record as the fastest pitcher to reach 200 strikeouts in a season (130 innings). He has one of the most unhittable fastballs in the Majors.

7. Oneil Cruz, SS, Pirates (age 23)
The tallest regular shortstop in big league history at 6-foot-7, Cruz is a unicorn who registered the hardest-hit ball (122.4 mph) in the Majors this season and led all players at his position in maximum (97.9 mph) and average (93.9 mph) arm strength. He also ranked in the top 10 percent among big leaguers in sprint speed (29.9 feet per second), barrel percentage (8.9) and average exit velo (91.9 mph).

8. Gabriel Moreno, C, Blue Jays (age 22)
The Blue Jays already have a 23-year-old All-Star catcher in Alejandro Kirk, but Moreno may be a better pure hitter and is a superior defender with significantly more arm strength.

9. C.J. Abrams, SS/2B, Nationals (age 21)
The best of the five prospects the Padres surrendered for Juan Soto, Abrams has struggled after being rushed to the big leagues but still has star tools with his bat-to-ball skills, elite speed and up-the-middle defense.

10. Spencer Torkelson, 1B, Tigers (age 22)
Torkelson was one of the toughest rookies to evaluate. Scouts considered the No. 1 overall selection in 2020 perhaps the best all-around offensive performer from the college ranks this millennium. Then he batted .203/.285/.319 with a 25 percent strikeout rate in his first season in Detroit after bashing 30 homers with a .935 OPS in his lone full Minor League season.

11. Alek Thomas, OF, Diamondbacks (age 22)
Thomas is a potential .300 hitter with at least 20-homer power -- and he's the third-best outfielder age 22 or younger in the Diamondbacks organization behind Carroll and Druw Jones.

12. George Kirby, RHP, Mariners (age 24)
Among big leaguers with 130 or more innings, only Kevin Gausman, Aaron Nola, Max Scherzer and Justin Verlander bettered Kirby in both strikeouts (9.2) and walks (1.5) per nine innings, a testament to his stuff and command.

13. Nick Lodolo, LHP, Reds (age 24)
Known more for his polish than overpowering stuff when the Reds drafted him seventh overall in 2019, Lodolo has improved the carry on his four-seam fastball and averaged 13.9 strikeouts per nine innings in the Minors and 11.4 in his rookie season.

14. Jeremy Peña, SS, Astros (age 24)
Peña swatted 22 homers during the regular season, became the first rookie shortstop ever to win a Gold Glove and the second rookie ever to win both Championship Series and World Series MVP awards. So why doesn't he rank higher? He's the second-oldest player on this list and scouts believe he has a lower offensive ceiling than the hitters ahead of him.

15. MacKenzie Gore, LHP, Nationals (age 23)
Another piece in the Soto trade, Gore logged a 1.50 ERA with 57 strikeouts in his first 48 innings, thriving with his fastball, before elbow inflammation began bothering him shortly thereafter.

The next 15:
16. Hunter Greene, RHP, Reds (age 22)
17. Shane Baz, RHP, Rays (age 23)
18. Nolan Gorman, 2B, Cardinals (age 22)
19. Shea Langeliers, C, Athletics (age 24)
20. Steven Kwan, OF, Guardians (age 24)
21. M.J. Melendez, C/OF, Royals (age 23)
22. Vaughn Grissom, 2B, Braves (age 21)
23. Reid Detmers, LHP, Angels (age 22)
24. Edward Cabrera, RHP, Marlins (age 24)
25. Roansy Contreras, RHP, Pirates (age 22)
26. Brayan Bello, RHP, Red Sox (age 23)
27. Bryson Stott, SS/2B, Phillies (age 24)
28. Vinnie Pasquantino, 1B, Royals (age 24)
29. Ezequiel Duran, 3B, Rangers (age 23)
30. Jhoan Duran, RHP, Twins (age 24)