Aledmys Diaz cardinals 2016
Cardinals shortstop Aledmys Diaz stands out as the early National League Rookie of the Year frontrunner. Getty Images

The 2016 Major League Baseball season is more than a quarter of the way complete, which provides enough of a sample size to assess the American and National League races for Rookie of the Year.

We’ve identified three top candidates from each league, based on overall performance and whether they’ve helped their clubs rise to the top of their respective leagues or divisions. Often ROY voters don’t necessarily focus on how big of an impact a rookie’s had on a team’s win-loss column, though last year they did with the Chicago Cubs’ Kris Bryant and the Houston Astros’ Carlos Correa each taking home honors and helping their teams reach the postseason.

It was much different in 2014, with New York Mets starting pitcher Jacob deGrom and Chicago White Sox first baseman Jose Abreu each posting excellent numbers that didn’t translate into team success.

As of now, this year’s potential candidates are on a mix of winning, struggling, or in-between squads, but they could turn their individual and team fortunes around over the next few months.

American League

Nomar Mazara, RF, Texas Rangers

The Rangers are presently 1.5 games back of the AL West lead, and Mazara’s played a huge role in their success with six home runs, 16 RBI, and 18 runs scored with a .303 average. “The Big Chill” is hitting for power and average, and he’s third among rookies with at least 100 at-bats in slugging percentage (.451). Mazara also has a strong arm, and voters care about defense.

Byung Ho Park, DH, Minnesota Twins

Ranking second among all rookies with nine home runs, the 29-year-old South Korean is one of the few bright spots in the last place Twins season. While Park's 47 strikeouts and .223 average are issues, he’s still third among AL rookies with a .798 on-base percentage.

Tyler White, 1B, Houston Astros

A poor batting average (.230) and 35 strikeouts are troubling, but White’s shown tremendous power with seven home runs and he leads all AL rookies with 18 RBI. He’s also tied with Park and Baltimore’s Joey Rickard with 12 walks, showing some patience at the plate that could lead to more dingers.

National League

Aledmys Diaz, SS, St. Louis Cardinals

The clear-cut frontrunner for the NL’s award, Diaz has excelled with a .345/.586/.962 slash line, is tops among rookies with 50 hits, and second with 24 RBI. The Cuban-born star has shown plate presence and aptitude beyond his years, even with St. Louis six games behind the Cubs for first in the NL Central. What may hold Diaz back is his defense mistakes (10 errors) at an important defensive position.

Trevor Story, SS, Colorado Rockies

After an amazing start, Story has clocked 12 home runs and knocked in 31 RBI, leading all rookies in both categories. He’s also second behind Diaz with 27 runs scored and a .924 OPS, and is playing a big role in Colorado’s fifth-ranked offense. Story's .892 OPS on the road should silence skeptics, too.

Steven Matz, SP, New York Mets

Fears over a serious elbow injury could’ve derailed what looks to be a promising ROY campaign for Matz. The 24-year-old has been tremendous for New York’s already stacked rotation, going 6-1 in seven starts with a 2.81 ERA and 43 strikeouts. The lefty has also walked just eight batters and posts an excellent 1.06 WHIP. Matz has been red hot since his terrible first start of the season, allowing just six earned runs in his last six starts.