They also make for a tough act to follow for this year's rookies.
By any measure, Trout and Harper were once-in-a-generation rookies. But that doesn't mean Major League Baseball's youth movement is a one-and-done deal.
The youngster with the potential to make the biggest impact this season was the cornerstone of one of the biggest offseason trades. Wil Myers, ranked No. 3 among MLB.com's Top 100 Prospects, was acquired by Tampa Bay from Kansas City last month. He has been lauded by many as the Minor League's best offensive prospect, having posted a .314/.387/.600 line with 37 home runs between Double-A and Triple-A last season.
Right-hander Jake Odorizzi, who went with Myers to the Rays in the trade, told Tampa Bay reporters to believe what's been said about the right-handed-hitting 22-year-old outfielder.
"Probably everything you've heard [about him] is pretty close to true," Odorizzi said. "I've played with him the past three years and he's incredible to watch. He's an exciting player, gap-to-gap power. He's a lot better defensively than most people make him out to be. ... He's got a strong arm, covers a lot of ground for a big guy and the hitting speaks for itself."
Although Myers' potential is tantalizing, he isn't considered the game's top overall prospect. That recognition, according to MLB.com, goes to Texas infielder Jurickson Profar.
Profar, who turns 20 in Spring Training, got a taste of the big leagues last season, playing in nine games. The natural shortstop is blocked at that position by Elvis Andrus, but incumbent second baseman Ian Kinsler could eventually shift to first base, clearing room for Profar.
The Rangers recently backed off that idea, after signing veteran Lance Berkman to be their designated hitter, but it's a move that nevertheless could be made.
Texas has another rookie, Mike Olt, who also could make an impact this year. The 24-year-old, MLB.com's No. 16 prospect, came up as a third baseman but because of Adrian Beltre, he is also blocked, at least for the time being. He could see time at first base, DH and the outfield corners.
In the National League, Travis d'Arnaud is baseball's top catching prospect (No. 11 overall) and will get a chance to take over behind the dish for the Mets, who acquired him from Toronto for reigning NL Cy Young Award winner R.A. Dickey.
Regardless of whether d'Arnaud makes the big club out of Spring Training, he's ready to make an impact whenever he gets the chance.
"I just try to focus on what I can control, just work hard and do as much as I can to become a better player each and every day," said d'Arnaud, who is approaching his 24th birthday and is with his third organization, having been traded by the Phillies in the Roy Halladay swap three years ago.
There are some other top prospects who could make this year's rookie class as exciting as that as of last year:
Trevor Bauer, MLB.com's No. 5 prospect, should benefit from his trade from Arizona to Cleveland. Indians general manager Chris Antonetti said the right-hander, who will turn 22 next week, "has some development left to do" and could open the season in the Minors.
Cardinals righty Shelby Miller (No. 19) appeared in six games for St. Louis last season and will compete with fellow youngsters Trevor Rosenthal (No. 60) and Joe Kelly for a rotation spot. Said manager Mike Matheny at the Winter Meetings: "The assignment we gave them going into this winter [was] show up to Spring Training ready to start and prove what you can do and have your arms built up to be ready to do that."
Braves righty Julio Teheran (No. 24) could open the season in Atlanta's rotation after appearing in two games, including one start, last season.
Pirates manager Clint Hurdle said 2011 No. 1 overall Draft pick Gerrit Cole (No. 7) and righty Jameson Taillon (No. 15) will have a chance to compete for a rotation spot in Spring Training.
Zack Wheeler (No. 6) should join fellow young righty Matt Harvey in the Mets' rotation at some point this summer.
Orioles right-hander Dylan Bundy (No. 2) likely will open the season in the Minors. But considering his quick ascent through the system last year, it wouldn't be surprising to see the 20-year-old in Baltimore at some point.