Rookies are exciting. They bring hope and energy to floundering teams while also providing a glimpse of what future the league may hold. First-time players in the NBA routinely struggle to adapt to the pace of the professional game, but there are always a few standouts every year who look and play like seasoned vets from the start.

Our rookie rankings here at numberFire are not subjective or influenced by the latest hype -- we put our faith and trust in our algorithms. Every two weeks, we’ll list the top five rookies in the Association based on our nERD metric, which measures a player's contributions based on efficiency, and indicates how many wins above or below .500 a player would make an average team over a full season. So while names like Lauri Markkanen, Donovan Mitchell and Lonzo Ball are in the conversation for Rookie of the Year Award (and rightfully so), you won't see them below, because their high volume of minutes and usage ultimately has rendered them less efficient, statistically speaking, than the players listed here.

To make sure we only include players regularly contributing to their team, we are limiting ourselves to considering rookies averaging at least 15 minutes per game.

Let's dive into the most efficient rookies with our top-five players of the 2017-18 season so far.

5. Ben Simmons, Philadelphia 76ers

nERD: 1.9
Previous Rank: 5

Since January 31st, Ben Simmons has taken a minor step back in the Philadelphia 76ers' offense. It has helped his game, though, which is reflected here. After posting a 23.5% usage rate in 35.0 minutes over the first 46 games, he has been on the court for just 33.9 minutes per game over his last seven contests, while carrying a usage rate of 20.9%. With the ball in his hands a tick less, he has been able to be more judicious with the rock, dropping his turnover rate to 15.5% (from 20.2%) while maintaining a similar assist rate of 33.1%.

During the span, his stat line has remained full, albeit a bit more trim. He is averaging 15.1 points, 6.4 rebounds, 7.1 assists, 2.3 steals, and 1.0 blocks over his last 7 games. He is the only rookie to sit in the top five in those specific categories, while being top dog in assists and steals.

His improved play has the 76ers on a roll, too -- they've won four of their last five and are sitting firmly in the playoffs. They are currently the 7 seed in the East, a full three games above ninth-place Detroit.

4. Jarrett Allen, Brooklyn Nets

nERD: 2.2
Previous Rank: 4

Over the last two weeks, Jarrett Allen has firmly planted himself as the Brooklyn Nets' center of not just the future but also the present. The 19-year-old has thrived since moving into a starting role, ranking eighth among all rookies in points (13.4), third in rebounds (7.1), and sixth in blocks (0.9) while playing an average of just 23.5 minutes over his last eight games. The rookies ranked ahead of him have all consistently seen over 32 minutes per night.

Allen has also been an efficient scorer thanks to his incredible percentages. During the past seven games, he is shooting 64.4% from the floor and 90.5% from the line. We can't chalk it up to minimal attempts since he has taken 8.4 shots from the floor and 3.0 from the charity stripe per game, both top-11 marks among first-year players.

Besides the 69.6% true shooting percentage, Allen has impressed on the glass, posting a 12.7% offensive and 16.9% total rebound percentage that's the best among all rookies who have played a least 20 minutes per night in the last two weeks.

3. Bam Adebayo, Miami Heat

nERD: 3.0
Previous Rank: 3

After a slow start, Bam Adebayo has settled into a prominent role in the Miami rotation as the first big off the bench. The 6'10" rookie has played at least 24 minutes in five of his last six games. Adebayo has even become the Heat's go-to center down the stretch, playing 8.5 minutes per game in the fourth quarter the previous two weeks. Head coach Eric Spoelstra is going with the rookie in crunch time over seasoned big man Hassan Whiteside. That makes sense since he owns a 95.2 defensive rating and 8.3 net rating in the second half of his last seven games.

On Tuesday night, Adebayo played the final 14:43 against the Toronto Raptors, helping the Heat nearly turn a 17-point deficit into a victory. The rookie did it all, racking up 5 points, 5 rebounds, 3 assists, and 1 block in the final quarter.

He finished the game with 11 points, his fourth double-digit scoring night in the last six games. Since January 31st, he has 3 double-doubles, a 6-assist night, and a current 5-game streak with at least 1 block. Adebayo is averaging 11.0 points, 7.6 rebounds, and 1.1 blocks in just over 24 minutes per night during this stretch.

2. John Collins, Atlanta Hawks

nERD: 3.3
Previous Rank: 2

A bit undersized, John Collins makes up for his lack of height with relentless energy and hustle without the ball.

The Atlanta Hawks' big leads all rookies in offensive (13.3%) and total rebound percentage (17.5%), while also ranking first in block percentage (4.2%). That boundless energy has been good and bad the last couple of weeks, as Collins grabbed double-digit boards twice, blocked four shots in only 23 minutes, and fouled out after just 18 minutes. He has also showcased his shooting touch this season, ranking in the top seven of all NBA players in field goal (58.4%) and two-point percentage (59.5%).

Between the rebounding, blocks, and high percentages, Collins ranks high in advanced metrics, leading all rookies in PER (20.0) and offensive win shares (2.6), while ranking second in win shares per 48 minutes (.163) and nERD.

1. Jayson Tatum, Boston Celtics

nERD: 4.1
Previous Rank: 1

As the Celtics have had their ups-and-downs the last two weeks, so has Tatum.

He kicked off February by dropping a career-high 27 points on 11-for-19 shooting in a nine-point Celtics win. He also posted a 29.6% usage rate, which another career-best mark. The rook attacked the basket, too, taking only one three-pointer (something that had just happened six times before). He put a bow on top of it all by swiping four steals on defense, as well. The all-around performance reminded us all why he has been a fixture at the top of our rookie ranking all year.

The last four games have been different story, though. The All-Star break couldn't be coming at a better time -- the rook has seemingly hit a wall, shooting 37.5% from the field and 16.7% from three, leading to him averaging fewer than 10 points (9.8) per game over the last week. That includes an embarrassing 2-for-9 shooting night for just 4 points in a 20-point loss to the Raptors.