The reinvention of the rookie was best illustrated by what happened the other night, when Mike Trout gave one of those postgame TV interviews, which usually trend toward the mundane, and uttered this decidedly bold declaration: "We're going to get to the playoffs," Trout said of his Angels. "I promise you that." Time was, such strong statements would best not come from the mouths of babes, for rookies were largely, with few exceptions, banned to the background, content to bide their time, do their time, earn their time.
Trout is obviously changing plenty of perceptions over what a young man can accomplish at the Major League level, as he is in the midst of perhaps the greatest rookie season in history, and is firmly at the forefront of the American League Most Valuable Player Award conversation. But Trout, who turned 21 just last week, is hardly the only young'un whose performance is pivotal for the playoff hopes of his club. Here are some others who are also instrumental, whether or not they're making playoff promises. Matt Moore, Rays: Remember the dominance Moore displayed against the Rangers in the AL Division Series last year and how that seemingly foretold of a fortuitous future? Well, the future is now. Moore has a 1.47 ERA in five second-half starts, and his surge, along with the return of Evan Longoria, has helped Tampa Bay rise. If Moore keeps this going, the Rays are -- once again -- going to be a handful down the stretch. Todd Frazier, Reds: Frazier is not alone in the relevant Reds rookie department. Cincinnati needs improved performance from shortstop Zack Cozart out of the leadoff spot, which has been a bit of a black hole from an on-base-percentage perspective. The Reds might bring up the already legendary Billy Hamilton for a September speed burst. But with Joey Votto still sidelined by a knee injury that required a second surgical procedure, and with Scott Rolen battling back issues, the versatile Frazier, who can man both corner-infield spots, has assumed a major role in the middle of the order. He's come through with a .302 average and .887 OPS thus far in August. Manny Machado, Orioles: Taiwanese import Wei-Yin Chen also merits mention, for, his last start aside, he's been an ace. But Machado is clearly the man of the moment. The O's received a few catcalls for calling this kid up after just 219 professional games -- none of them above Double-A. But by the end of his first weekend in the big leagues, Machado was routinely hearing his name chanted and was making curtain calls. He became the first 20-year-old to hit three home runs in his first four Major League games. Machado has filled a huge hole at third base for an club that entered the week in possession of the second AL Wild Card. Baltimore needs him to keep the curtain calls coming. Wade Miley, D-backs: I just wrote a bit about Miley's personality, but it's his performance that carries the most weight for an Arizona team that still has the opportunity to assert itself in the National League West. With a 12-8 record and a 3.02 ERA, Miley has been the best thing the D-backs have had going for them in the rotation. They'll clearly need that to continue. Yoenis Cespedes, A's: The Athletics are where they are largely because of the first-year exploits of the likes of Tommy Milone (9-9, 3.91 ERA) and Jarrod Parker (7-6, 3.55) in their strong rotation and Ryan Cook (2.72) in the late innings. But the rookie who has arguably held the greatest import is Cuban import Cespedes, who has hit .306 with an .876 OPS. Hand and wrist issues have limited him to 81 games, but in those games, the A's are 49-32. In their other 33 games, they are 12-21. That says it all. Starling Marte, Pirates: By hitting a homer on the first big league pitch he saw, Marte set an impossible standard for himself. That was a tough act to follow, but Marte did go deep three other times through his first 76 plate appearances. He's provided some improvement at what had been a lackluster leadoff spot for the Bucs, and he's also made an impact with his arm in the outfield. Improved plate discipline from Marte would be a huge help for a Bucs team trying to reach the postseason for the first time in two decades. Yu Darvish, Rangers: With his feisty, game-winning pinch-hit single against the Tigers the other night, Mike Olt gave us a glimpse of why Texas was so protective of him at the Trade Deadline. And Robbie Ross has, on the whole, helped the bullpen. But the most important rookie on the Rangers' roster remains Darvish. The injuries that removed Colby Lewis and Neftali Feliz from the rotation and the ineffectiveness that led to Roy Oswalt's demotion put all the more emphasis on the need for a strong stretch run from Darvish. He is 2-3 with a 7.11 ERA in the second half, but he earned his first win in more than three weeks on Sunday, so that's a start. Bryce Harper, Nationals: Ian Desmond's oblique injury opened a second-base starting opportunity for Steve Lombardozzi, so he's a rookie worth watching. But no NL rookie attracts more attention than Harper, and his significant slide since mid-June, while certainly understandable for a 19-year-old, has to be cause for concern. The Nats have the most wins in baseball and just rattled off eight straight, but a return to early-season output from Harper would go a long way toward helping them lock up the NL's top seed and advance in October. As it stands, Harper entered Tuesday with a .211 average in his last 53 games, and a .167 average in his last 24. Quintin Berry, Tigers: Berry's role has been limited by the return of Andy Dirks. Berry is now more of a late-inning defensive replacement and pinch-hit specialist. But on a Detroit team that is slow by design, one sees how even a bench player like Berry and his speed and defense can have a big role in the close confines of the AL Central race. We can also look at a Tigers team that has gotten just a .646 OPS out of right field and a .667 OPS from the DH spot and see how Double-A prospect Nick Castellanos could get a late-season call.
Anthony Castrovince is a reporter for MLB.com. Read his columns and his blog, CastroTurf, and follow him on Twitter at @Castrovince. This story was not subject to the approval of Major League Baseball or its clubs.