As this year's Hall of Fame class would attest, future stars don't always shine as rookies. In 1987, Greg Maddux was the worst starter on another last-place Cubs team, going 6-14 with a 5.61 ERA and a 1.638 WHIP that each would have ranked as the worst in baseball had he not fallen just short of qualifying.
Meanwhile in Atlanta, another second-round pick from the 1984 draft spent his first summer in the big leagues getting battered. Tom Glavine went 2-4 in nine starts, with an ERA (5.54) and WHIP (1.748) not much different from Maddux's. Neither received a vote in the National League Rookie of the Year balloting -- Benito Santiago was the unanimous winner -- but that didn't stop them from combining for 660 victories, six Cy Young Awards, a 1995 World Series title with the Braves and a joint induction in Cooperstown this July.
With that in mind, we've decided to rank baseball's best dozen rookies based on their long-term impact. Not on how they've done this season -- just one of our top five picks is likely to garner a Rookie of the Year vote -- but on how good they'll be in the long run. We considered only players who have lost or are a lock to lose their rookie status in 2014, which is why Mariners right-hander Taijuan Walker and Cubs outfielder Jorge Soler aren't mentioned.
1. Masahiro Tanaka, RHP, Yankees (age 25). He hasn't pitched since July 8, and he may or may not need Tommy John surgery. But even if Tanaka's elbow requires reconstruction, the track record suggests that he'll be able to reclaim the form that allowed him to go 12-4, 2.51 with a 135/19 K/BB ratio in 129 1/3 innings. The $155 million man's splitter might be the most unfair pitch in the world, and his fastball and slider aren't bad either.
2. Xander Bogaerts, SS/3B, Red Sox (age 21). After looking advanced well beyond his years while helping Boston win the 2013 World Series, he and the rest of the Red Sox have looked overmatched for much of this season. As disappointing as Bogaerts' performance has been, the most important number is 21 -- his age. He has hit much better when Boston has left him at his natural position, and he still has the bat speed and advanced approach to become a 30-homer shortstop who can provide average defense.
3. Oscar Taveras, OF, Cardinals (age 22). The consensus best pure hitter in the minor leagues before St. Louis called him up in May and again for good in July, he hasn't exactly taken the majors by storm. As with Bogaerts, it's important to remember that Taveras is young and loaded with ability. Big leaguers have used his ability to make hard contact on pitches outside the strike zone against him by getting him to chase more than he should, but once he settles down, he could develop into a future batting champion capable of providing 20-plus homers per season.
4. Gregory Polanco, OF, Pirates (age 22). He has the best all-around tools on this list and he probably should have been Pittsburgh's starting right fielder on Opening Day. Polanco only has two hits in 37 big league at-bats since Aug. 12, which has wrecked his rookie numbers, but before that he was showing glimpses of his above-average power and speed and he has done a reasonable job of controlling the strike zone. He's still a 25-25 man waiting to happen.
5. Javier Baez, 2B/SS, Cubs (age 21). His bat speed, power and aggressive approach all achieved near-legendary status in the minors, and they've all been on display since he arrived in Chicago in August. Baez has cooled off since going deep three times in his first three games, and he could finish with more homers than walks and more extra-base hits than singles while striking out in nearly half his at-bats. Though he'll have to make some adjustments at some point, he should contend for home run titles with fellow Cubs Kris Bryant, Anthony Rizzo and Soler.
6. George Springer, OF, Astros (age 24). Unlike the four position players ahead of him on this list, Springer has pretty much lived up to expectations as a rookie. Though he has been out since mid-July with a left quadriceps injury, he slugged 20 homers in half a season and showed he could be dangerous despite piling up strikeouts. His tools are quite similar to Polanco's, though the latter will be a bit more consistent at the plate because he makes more contact.
7. Jose Abreu, 1B, White Sox (age 27). No, we're not ignoring the facts that he'll walk away with all of the Rookie of the Year awards or that numerous teams are kicking themselves for not topping Chicago's $68 million contract offer. Abreu has answered questions about whether his power would play at the major league level by producing consistently all season and 21 of his 33 homers have come away from hitter-friendly U.S. Cellular Field. The reasons he ranks only seventh on his list are that he's the oldest player and already in his prime, and that he's a first baseman and all of the other hitters mentioned are capable of playing up the middle.
8. Mookie Betts, OF/2B, Red Sox (age 21). After a lackluster pro debut in 2012, he broke out the following season and then greatly exceeded expectations again this year, reaching Boston in June and posting the second-best OPS on the club (behind only David Ortiz). Betts doesn't have the same ceiling or thunder in his bat that the guys ahead of him on this list do, but he has a higher floor than many of them and surprising pop at 5-foot-9. He's a gifted hitter with mastery of the strike zone, plus speed and the defensive versatility to play several positions.
9. Marcus Stroman, RHP, Blue Jays (age 23). Michael Wacha wasn't the only college pitcher who fell further in the 2012 draft than he should have. Stroman, Duke's first-ever first-rounder, lasted 22 picks because too many clubs focused on his height (5-foot-9) rather than his electric stuff (headlined by a wipeout slider and a 92-96 mph fastball). He has been Toronto's best starter since he joined the rotation in late May, recording 13 quality starts in 18 tries and spinning a 93-pitch shutout against the Cubs on Monday, and that should continue going forward.
10. Yordano Ventura, RHP, Royals (age 23). In his first big league game last September, he threw a 102.8-mph fastball, the fastest pitch thrown by a starter in 2013. Ventura has continued to bring the heat this year, averaging an MLB-high 96.9 mph (according to Fangraphs) with his fastball. He has been as strong as ever in August and September, giving Kansas City a chance to end its 29-year playoff drought. If he can continue to improve his command and his secondary pitches, he'll be a frontline starter.
11. Kevin Gausman, RHP, Orioles (age 23). The first pitcher drafted in 2012 and the first starting pitcher from that class to make it to the majors, he struggled with Baltimore last season but has been critical to the team's efforts in all but locking up the American League East in 2014. Gausman has done a much better job commanding his stuff in his second year in the big leagues, pitching primarily off his mid-90s fastball and his splitter/changeup. It will be fun watching him duel Dylan Bundy for the distinction of the Orioles' No. 1 starter in coming years.
12. Billy Hamilton, OF, Reds (age 24). Though he still has a lot of work to do at the plate, the quickest player in the majors has had a solid rookie season. Hamilton has been a valuable defender in center field in only his second year playing the position, and he has stolen 55 bases -- a number that could easily double if he enhances his on-base ability and improves his reads and jumps. He already has set a career high with seven homers, but he needs to focus on making contact so he can wreak more havoc with his speed.
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Jim Callis is a contributor to Sports on Earth. He has been covering prospects and the draft since 1988, when he began the first of two long stints at Baseball America. He joined MLB.com and MLBPipeline.com in September 2013.