When 20-year-old Cardinals outfielder Jordan Walker took the field in St. Louis Thursday, he became the first player born in the year 2002 or later to play in the Major Leagues.

MLB's No. 4 prospect is the youngest player to make an Opening Day roster this year, and he takes the distinction with quite a bit of clearance, as he's nine months and 21 days younger than the second-youngest player, Ezequiel Tovar.

The 18 youngest players on Opening Day rosters this year are all position players. In fact, 20 of the first 21 players on the list are hurlers. Arizona has the largest presence, fielding five of the youngest 25 players on Opening Day, headlined by MLB Pipeline's No. 2 overall prospect Corbin Carroll, who opens the year as the 10th-youngest player at 22 years, seven months and nine days.

• Top prospects on Opening Day rosters | Where Top 100 prospects are starting the season | Rookie power rankings

MLB's 2022 Rookies of the Year, Julio Rodríguez and Michael Harris II, as well as former No. 1 overall prospect Wander Franco are all among MLB's seven youngest players entering this season, despite their already impressive resumes.

1. Jordan Walker, 3B/OF, Cardinals (age 20, DOB: May 22, 2002)
Since being taken in the first round of the 2020 Draft by the Cardinals (No. 21 overall), all Walker has done is hit the cover off the ball. He posted averages above .300 and slugging percentages above .500 in each of his first two full Minor League seasons, and was the youngest player in Double-A last year. MLB's No. 4 overall prospect never played a second in Triple-A when he forced his way to St. Louis this spring. The last time the Cardinals brought up a player who never played at Triple-A -- 2001, a 21-year-old named Albert Pujols.

2. Ezequiel Tovar, SS, Rockies (age 21, DOB: Aug. 1, 2001)
Tovar appeared in nine Major League games at the conclusion of last season -- batting .212 with a home run -- but his Major League debut probably would have occurred much sooner if not for a left hip injury that sidelined him for six weeks while he was at Double-A Hartford. But the glove-first shortstop showed he can more than hold his own at the plate, batting .302 with two dingers, a pair of doubles, eight RBIs and nine runs scored in 20 games this spring.

3. Gunnar Henderson, SS, Orioles (age 21, DOB: June 29, 2001)
The American League Rookie of the Year favorite as we entered play Thursday, it's hard to believe that Henderson started last year at Double-A. But his play shot him up the Orioles' ranks and he made his debut in The Show on Aug. 31, 2022. In 34 games with Baltimore last season, MLB's top overall prospect showcased his elite talent -- collecting 30 hits (12 for extra bases), while driving in 18 runs and scoring 12 times. He also instantly became a walking highlight reel, posting a .990 fielding percentage.

4. Anthony Volpe, SS, Yankees (age 21, DOB: April 28, 2001)
The Yankees’ first-round Draft pick (No. 30 overall) in 2019, Volpe became the Minors’ first 20-homer, 50-steal player since 1996 (Andruw Jones) last year while finishing the season with 22 games at Triple-A. Considered a long shot to break camp with the Yankees, MLB's No. 5 overall prospect forced the organization's hand with his performance, batting .309 with 10 extra-base hits in 19 Grapefruit League games. He was the youngest player to start a Yankees season opener since Derek Jeter in 1996.

5. Michael Harris II, OF, Braves (age 22, DOB: March 7, 2001)
Despite missing the season's first two months last year, Harris made his impact felt immediately upon his return. He led all NL rookies with a 5.3 bWAR, including 4.4 offensive WAR and 1.3 defensive WAR. He also racked up 19 home runs and 20 stolen bases. He finished tied for fourth among all center fielders with eight Defensive Runs Saved. The 22-year-old looked great this spring, slashing .292/.358/.542 with two homers, two triples, a pair of doubles and nine RBIs over 18 Grapefruit League games.

6. Wander Franco, SS, Rays (age 22, DOB: June 1, 2001)
Injuries have slowed Franco's progress through his pro career, and that's saying a lot considering he's still only 22. After bursting into the Major League-spotlight in 2021, slashing .288/.347/.463 through his first 70 games in The Show, Franco had a slow start to last season before missing two months with a right wrist injury. He returned and hit .316 last September, but right quad tightness limited the shortstop to eight games this spring. However, he is healthy again and clubbed a homer as the No. 2 hitter for the Rays on Thursday.

7. Julio Rodríguez, OF, Mariners (age 22, DOB: Dec. 29, 2000)
Rodríguez left very little doubt in the mind of ROY voters last season, after he led all rookies in home runs (28), OPS (.853), wRC+ (146) and total bases (260). He ranked second among rookies in RBIs (75), runs scored (84) and stolen bases (25), while finishing third in hits (145). He also became only the second rookie (Mike Trout in 2012 the other) with at least 25 home runs, 25 stolen bases and an .800 OPS. The AL Silver Slugger Award winner is primed for an encore performance.

8. C.J. Abrams, SS, Nationals (age 22, DOB: Oct. 3, 2000)
Abrams appeared on this list last year as the third youngest, after getting the call to replace an injured Fernando Tatis Jr. in San Diego. Abrams only slipped five spots but his experience in the bigs will be massive this season for the Nats. After being dealt to the nation's capital at the Trade Deadline as part of the mammoth haul for Juan Soto, Abrams finished the year appearing in 44 games for the Nats. After going 4-for-4 in swipe attempts during Grapefruit League play, Abrams is poised to provide a spark in Washington's lineup.

9. Riley Greene, OF, Tigers (age 22, DOB: Sept. 28, 2000)
Greene spent a stint as MLB's No. 2 overall prospect last season before getting called up to Detroit on June 18, 2022. He played well enough to stick in Motown, batting .253 with five homers, four triples, 18 doubles, 42 RBIs and 46 runs scored over 93 games while exhibiting elite defense in center field, posting a .992 fielding percentage. Greene looked more comfortable at the plate this spring, slashing .308/.345/.615 with four dingers in 19 games and batted third for the Tigers.

10. Corbin Carroll, OF, D-backs (age 22, DOB: Aug. 21, 2000)
Carroll is the clear front-runner for NL Rookie of the Year after proving he belonged during his big league debut last year. MLB's No. 2 overall prospect showed he had little left to accomplish in the Minors last season after posting a 1.035 OPS, mostly between Double-A and Triple-A. In addition to his blazing 70-grade speed, Carroll is one of the best pure hitters in the game -- he batted .370/.508/.630 across 18 Cactus Leagues games this spring.

11. Bobby Witt Jr., SS, Royals (age 22, DOB: June 14, 2000)
Another player making a second straight appearance on this list, Witt was fourth last year and was the youngest Royal ever to make his big league debut on Opening Day. In that game, he smoked a game-winning double while also showing off his plus-plus speed and arm strength. He went on to finish fourth in Rookie of Year voting with one second-place vote and four third-place votes. This spring, Witt picked up where he left off, slashing .345/.344/.552 and batted leadoff for Kansas City.

Others:
12. Luis Garcia, SS, Nationals (age 22, DOB: May 16, 2000)
13. Nolan Gorman, 2B, Cardinals (age 22, DOB: May 10, 2000)
14. Alek Thomas, OF, D-backs (age 22, DOB: April 28, 2000)
15. Gabriel Arias, SS, Guardians (age 23, DOB: Feb. 27, 2000)
16. Gabriel Moreno, C, D-backs (age 23, DOB: Feb. 14, 2000)
17. Logan O'Hoppe, C, Angels (age 23, DOB: Feb. 9, 2000)
18. Triston Casas, 1B, Red Sox (age 23, DOB: Jan. 15, 2000)
19. Ryan Weathers, LHP, Padres (age 23, DOB: Dec. 17, 1999)
20. Brice Turang, SS, Brewers (age 23, DOB: Nov. 21, 1999)
21. Miguel Vargas, 3B, Dodgers (age 23, DOB: Nov. 17, 1999)
22. Roansy Contreras, RHP, Pirates (age 23, DOB: Nov. 7, 1999)
23. Mason Englert, RHP, Tigers (age 23, DOB: Nov. 1, 1999)
24. Geraldo Perdomo, SS, D-backs (age 23, DOB: Oct. 22, 1999)
25. Carlos Vargas, RHP, D-backs (age 23, DOB: Oct. 13, 1999)
26. Gregory Santos, RHP, White Sox (age 23, DOB: Aug. 28, 1999)
27. Spencer Torkelson, 1B, Tigers (age 23, DOB: Aug. 26, 1999)
28. Hunter Greene, RHP, Reds (age 23, DOB: Aug. 6, 1999)
29. Ji Hwan Bae, 2B, Pirates (age 23, DOB: July 26, 1999)
30. Jarred Kelenic, OF, Mariners (age 23, DOB: July 16, 1999)