The All-Star rosters have been announced and all 30 teams are reaching the midway point of the 162-game marathon. That means there's no better time to take a look back at what has been a very eventful and historic three months in Major League Baseball. Today, we'll narrow it down to the rookies and take a look at the 10 who have made the biggest impacts during the first half of the 2012 season.Mike Trout — Los Angeles Angels
.340 AVG, .947 OPS, 10 HR, 36 RBI, 22 SB
The 20-year-old outfielder has been a human highlight reel and a spark plug since his recall and insertion into the Angels lineup on April 28. Prior to that date, Los Angeles was 6-14 and struggling to gain traction in the American League West. Since, they are 39-22, and are now positioned to push Texas in the division and compete for a wild-card spot. There's little doubt Trout's immediate impact is a major reason for the turnaround, and his continued development into a superstar will make them a dangerous foe come October.
2. Wade Miley — Arizona Diamondbacks
9-4, 2.87 ERA, 66 K in 94 IP
Arizona's 2008 first-round draft pick started the season on fire, earning the National League Rookie of the Month for April — and he hasn't slowed down much since, helping his squad overcome the struggles of Ian Kennedy and injuries to Joe Saunders and Daniel Hudson. He's an All-Star, and he's currently the odds-on favorite for National League Rookie of the Year, but will have to hold off some stiff competition in the second half.
3. Yu Darvish — Texas Rangers
10-5, 3.57 ERA. 117 K in 102.2 IP
Darvish arrived in the United States with plenty of hype, and so far he's lived up to that hype by effectively sliding into the role of staff ace in Texas. The only downside so far is that he will struggle with his command for extended stretches — he's currently third worst among American League starters with 53 walks — but he's also among the league leaders in strikeouts and hasn't been killed by the long ball — only nine allowed — at the very hitter-friendly Ballpark in Arlington.
4. Will Middlebrooks — Boston Red Sox
.298 AVG, .873 OPS, 10 HR, 37 RBI
How good has Middlebrooks been for Boston? The Red Sox were forced to use gold glove first baseman Adrian Gonzalez in the outfield just to keep his name in the lineup and ultimately shipped longtime favorite Kevin Youkilis to the Chicago White Sox to open up a regular spot. That's some serious impact. I also recently heard someone mention that Middlebrooks effectively Wally Pipp-ed Youkilis, and for the first time in a long time I didn't roll my eyes when hearing that clichéd analysis.
.276 AVG, .834 OPS, 8 HR, 23 RBI, 8 SB
Not a lot separates Bryce Harper from Trout from a talent standpoint, but Washington's phenom certainly knows how to garner the attention off it as well. That aside, in two short months at the big-league level, Harper put himself right into the the Rookie of the Year and All-Star discussion. And though he hasn't yet been named to this season's Midsummer Classic, you safely ink his name into several future appearances based on what we've seen so far.
6. Jarrod Parker — Oakland Athletics
5-3, 2.46 ERA, 61 K in 81.1 IP
Signing fellow rookie Yoenis Cespedes was Billy Beane's splashy offseason acquisition, but it looks like he found another gem in Jarrod Parker, who came over from Arizona as a part of the big Trevor Cahill deal. Through his first 13 big-league starts, Parker has allowed two runs or fewer in nine of them. Only Dwight Gooden can make that same claim since 1918. And yes, a lot of that has come at one of the cozier venues for pitchers, the Oakland Coliseum, but his stuff looks like it would hold up anywhere.
7. Robbie Ross — Texas Rangers
6-0, 1.03 ERA, 26 K in 43.2 IP
The 23-year-old left-hander started the season unlike any other rookie in history, notching a victory in four of his first six relief appearances. He hasn't stopped being dominant since. In fact, Ross is currently on a 19 1/3 inning scoreless streak over his last 13 appearances, and hasn't allowed an earned run in 18 appearances dating back to May 17. That's a pretty special run, and the fact that he can fill several roles — could move to the rotation at any time — gives Ron Washington some very intriguing options with his pitching staff.
5-5, 4.17 ERA, 93 K in 95 IP
The numbers aren't as pretty as many anticipated, but they're trending in the right direction after Moore struggled through a rough first six weeks. In fact, they look really, really good now compared to then. And despite those struggles, he's still striking nearly one batter per inning in the toughest division in baseball. It's probably too late for him to make a run at Trout for AL Rookie of the Year, but he could easily be the top rookie from here on out.
9. Yoenis Cespedes — Oakland Athletics
.276 AVG, .834 OPS, 9 HR, 35 RBI
When Cespedes has remained on the field, he has been just as dynamic as any of the rookies listed above him. Unfortunately, a nagging hamstring injury has limited him to 49 games. Still, the flashes of brilliance and game-changing ability we've seen in those games has done nothing but whet our appetite for what's to come from this five-tool athlete once he's finally 100 percent.
10. Wilin Rosario — Colorado Rockies
.247 AVG, .813 OPS, 14 HR, 36 RBI
If you like your catcher's strong and athletic, then you'll love Wilin Rosario. He's currently leading all rookies in home runs despite playing only eight games in April, and that lead could continue growing now that he's taken Colorado's starting job away from the injured Ramon Hernandez. He is some kind of strong — 25-30 home run potential — and runs very well for his position. The downside: He still has a ways to go defensively and absolutely refuses to walk. But man, that power.
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