Last year, the American League Rookie of the Year race was a two-man competition between Jose Abreu and Masahiro Tanaka. As Tanaka fell behind due to injury woes, Abreu ran away from the competition.

Abreu was not only the best AL rookie last year: he was also among the best hitters in the Majors, winding up with an fWAR of 5.3.

This year, the AL Rookie of the Year race is a bit different. While nobody's running away with the award like Abreu did or performing as well as he did last season, there's still a number of great candidates. Two shortstops and a starting pitcher headline the AL rookie class, many of whom weren't even called up till midseason. 

So with a little more than four weeks left in the regular season, here are the leading contenders for AL Rookie of the Year in 2015. We'll use numberFire's nERD metric, used to measure of runs a player contributes, or in the case of a pitcher, prevents, above or below the league average during the course of a full game, along with a few other sabermetrics to determine the leading candidates for the award.

7. Roberto Osuna, RP, Toronto Blue Jays

nERD: 1.06 | fWAR: 1.7

Roberto Osuna has helped stabilize a bullpen that was among the worst in the MLB last season. Osuna has taken over as the Blue Jays closer this year and recorded 15 saves in 16 chances, while also recording 7 holds. For the season, Osuna has a 1.91 ERA, 2.28 FIP and 3.30 xFIP with 10.01 K/9 and 1.91 BB/9. As a reliever, Osuna has posted a 1.7 fWAR, which ranks tied for sixth among all AL rookies and third among pitchers. 

Osuna took over the closer role for the Blue Jays midseason and has performed fantastically. Since his first recorded save on June 22, Osuna has a 1.46 ERA, 2.28 FIP and 2.80 xFIP, allowing just four earned runs as the Blue Jays closer and solidifying Toronto's bullpen for a probable postseason run.

6. Devon Travis, 2B, Toronto Blue Jays

nERD: 1.16 I fWAR: 2.3

For a while, and before two AL shortstops were called up from the minors, Devon Travis was leading the AL Rookie of the Year race. The Blue Jays second baseman was hitting .304/.361/.498 with a .371 wOBA and 137 wRC+, posting a 2.3 fWAR. Even after missing time with injury early on in the season, Travis was a revelation for the Jays at second base. 

But then Travis re-injured his shoulder and was placed on the 15-day disabled list with no timetable to return. And after receiving another cortisone shot on August 25, it's looking like Travis might not return this year. With just a few weeks left in the regular season, Travis might not play again this year, and may have lost his shot at the AL Rookie of the Year.

5. Trevor May, P, Minnesota Twins

nERD: 1.50 I fWAR: 2.1

In and out of the bullpen, Trevor May has performed amicably for the Twins. In 34 games (16 starts) May has a 3.96 ERA, 3.22 FIP and 3.87 xFIP with 8.27 K/9 and 2.02 BB/9. And with a .339 BABIP, May has been getting unlucky but has still been able to leave 73.2 percent on runners on base. 

Now back in the rotation due to injury, our algorithms project projects May to regress over the rest of the year, posting a 4.78 ERA. If May does regress, he'll play himself out of the AL Rookie of the Year race, but if not, a few good starts could move him back right in the thick of things.

4. Miguel Sano, DH, Minnesota Twins

nERD: 1.62 | fWAR: 1.7

Called up on July 2, Miguel Sano has been incredible and has somehow managed to post a 1.7 fWAR in just under two months. In 189 plate appearances, Sano is hitting .287/.397/.592 with a .418 wOBA and 171 wRC+. Sano's been a monster in the Twins lineup, already showing his power with a .592 slugging percentage, .306 isolated power (ISO) and 12 home runs in a less than two-month span.

But with a .413 BABIP and 35.4 K%, Sano might have trouble keeping it up as the season continues. With his BABIP and an astounding 34.3% HR/FB ratio, our algorithms project Sano to regress mightily in September and hit just .224/.333/.469 with a .351 wOBA. But even so, his numbers would still be incredible for the rookie and would keep him in the thick of the AL Rookie of the Year hunt.

3. Lance McCullers, SP, Houston Astros

nERD: 1.34 | fWAR: 2.3

After making his Major League debut for the Astros in May, Lance McCullers has been a revelation for Houston with a 3.12 ERA, 2.82 FIP and 3.42 xFIP in 15 starts for the AL West leader. In 83.2 innings, McCullers is averaging 9.36 K/9 and 3.01 BB/9 while posting a 2.3 fWAR, best among American League rookie pitchers. 

But in the second half, McCullers, a rookie who hadn't thrown more than 104 innings in a season, has come back to earth with a 5.12 ERA, 3.44 FIP and 3.44 xFIP in 19.1 IP. McCullers was sent down to Double A to get some rest and figure himself out. 

And after being called up earlier this month, McCullers improved in his first start back, throwing 7.0 innings with 2 earned runs and 8 hits. If the right-hander can continue to put up good innings, and the Astros don't put him on a innings limit, McCullers could find himself throwing for the AL Rookie of the Year.

2. Francisco Lindor, SS, Cleveland Indians

nERD: 0.30 | fWAR: 2.3

Francisco Lindor, who made his debut just over two months ago, has been incredible for the Cleveland Indians both at the plate and in the field. After struggling early on Lindor is hitting .306/.341/.433 with a .334 wOBA and 114 wRC+, posting a 2.3 fWAR in just over two months. And after starting slow, Lindor's really come on in the month of August hitting .378/.410/.511 with a .394 wOBA and 156 wRC+. Unfortunately for Indians fans, with a .343 BABIP, Lindor will probably regress at the plate, as our algorithms project him to hit .269/.329/.359 with a .302 wOBA for the rest of the season.

But that's not where majority of Lindor's value lies. Lindor was never expected to this good of a hitter this early on. His value lies in his spectacular fielding, with which he's made many great plays at shortstop. In just over 557.0 innings at short, Lindor has become one of the best shortstops in the league and among the best in the AL. His 14.9 UZR/150 ranks second in the AL, while his 4 defensive runs saved and 4.9 UZR rank third. And per FanGraphs inside edge fielding, he's made 75 percent of the unlikely plays at short, those that have between a 10 and 40 percent chance of being fielded. 

In the Majors for just over two months, Lindor's played himself right into the AL Rookie of the Year race, and if he continues to hit and field at his pace, he just might have a shot at winning it.

1. Carlos Correa, SS, Houston Astros

nERD: 1.47 | fWAR: 2.8

It was only a matter of time when Carlos Correa was called that he'd start mashing and moving himself into the favorite for the AL Rookie of the Year. The Astros' shortstop has been the best rookie hitter in the AL this year, hitting .278/.347/.510 with a .368 wOBA and 136 wRC+, posting a 2.8 fWAR, best among all AL rookies. Correa's been a monster at the plate hitting 15 home runs with a .232 ISO, and he's been doing it without getting real lucky, with just a .299 BABIP. 

If Correa can keep hitting this season, not regressing too much, he should win the AL Rookie of the Year award because of his hitting prowess, even if his fielding doesn't stack up against Lindor's. But both ZiPS and numberFire's projection predict a substantial regression for Correa in September, ZiPS projecting Correa to have a .319 wOBA and 103 wRC+ the rest of the season, while numberFire's projections have Correa putting up a .322 wOBA the rest of the year. 

If Correa does regress, September will be a dogfight between he, Lindor, McCullers, and possibly even Sano for the AL Rookie of the Year award.