Small ball is all the rage in today's NBA.

So, you'd think it would be easier to define.

The term conjures a simple image to most: namely, a five-man unit without a traditional center in the middle. But the concept revolves around versatility, which often requires the absence of size to be fully maximized.

There are different ways to build a do-it-all small-ball lineup, though, which makes an exercise like this tricky.

While we could rigidly hold onto traditional position designations and use them to set our field, that might leave us with too many one-trick 4s or an unnecessary exclusion of a versatile 5. Instead, we're using more of a "know it when you see it" designation to capture all the different variations this style has spawned.

As for ranking 2019-20's best small-ball lineups, we're zeroing in on those that have logged at least 50 minutes. To avoid redundancy, we're only analyzing one fivesome per squad. Finally, our aim for objectivity involves ranking each quintet by what we're calling their "lineup score," which is their net rating and minutes played multiplied together to account for both efficiency and volume.

Javair Gillett, Director of Athletic Performance for the Houston Rockets, joins The Full 48 with Howard Beck to discuss how the Houston Rockets as an organization working with players on training and nutrition during the NBA shutdown, his thoughts on what it will take to get players in game-shape once the season resumes, and some of the tips he’s providing to players.

5. Oklahoma City Thunder (Lineup Score: 1705.6)

Lineup: Chris Paul | Dennis Schroder | Shai Gilgeous-Alexander | Danilo Gallinari | Nerlens Noel

Net Rating: Plus-20.8 net rating over 82 minutes

Just like Thunder head coach Billy Donovan, we're willing to take an unconventional approach with these five. While some might disqualify them from a small-ball discussion given this 6'10" frontcourt combo of Danilo Gallinari and Nerlens Noel, we'll allow it for a few reasons.

Gallinari has a guard's game, and his scorching-hot three-ball (42.1 percent since the start of last season) adds optimal spacing from the 4 slot. Noel has a wing's agility, so even if he's a rim-runner on offense, he gives the defense the kind of switchability everyone seeks in a small-ball lineup.

And oh yeah, Paul, Schroder and Gilgeous-Alexander are all point guards. It wasn't long ago that dual-point guard groupings were considered pushing the envelope, but Donovan set the envelope (and the hoops world) on fire with this three-headed monster. The three floor generals own an absurd plus-28.6 net rating over their 401 minutes together, the Association's highest efficiency mark of all trios to log 150-plus minutes.

"Most teams have one or two really good defenders," Gilgeous-Alexander told SB Nation's Michael Pina. "It's rare you find a team with three really good defenders. It's hard for them to guard all three of us at the same time."

The three point guards can all create for themselves or their teammates. Gallinari is both a capable shot-creator and a knockdown sniper. All four rank among the 74th percentile in spot-up shooting. Noel doesn't help there, but he's a massive asset in the screen game as a 91st percentile roller.

This may not look like the normal small-ball grouping, but the two-way versatility is all the same.

4. Houston Rockets (LS: 1754.8)

Lineup: Russell Westbrook | James Harden | Danuel House Jr. | Robert Covington | PJ Tucker

Net Rating: Plus-10.7 net rating over 164 minutes

Most NBA lineups look down on this one, and not in a disrespectful manner. It's just that the hoops world hasn't seen a commitment to pint-sized play quite like this.

The Rockets had a sturdy center in 6'10", 240-pound Clint Capela, who had established a top-10 floor at the position and flashed top-five upside. But his offensive range didn't reach beyond the restricted area, which clogged the runway when Russell Westbrook and James Harden went on the attack—a common occurrence, as they rank first and seventh, respectively, in drives per game.

So, Capela was shipped out, Robert Covington was brought in and PJ Tucker was promoted to full-time center. Now, the Rockets have four reliable snipers around Westbrook, whose full-throttle style has never looked better. In 11 games after the trade, the Brodie erupted for 31.7 points on 54.6 percent shooting.

"It's opened up the floor for Russ to use his speed, which has made it a good thing," Rockets development coach John Lucas said, per Jonathan Feigen of the Houston Chronicle. "We all accepted that, to let Russ be him. That's what he's done. He could not find his groove and niche early. Once he figured out what it was, we were really shooting the ball well, which made it a highway for him."

Harden and Russell are first and second, respectively, in isolation scoring, which nets Houston with 22.8 points per night. House, Covington and Tucker are all versatile defenders who also give the Rockets a combined 5.7 catch-and-shoot threes per game.

This group might struggle on the glass (46.6 rebounding percentage), but it's so good in other areas that it hasn't mattered yet.

3. Miami Heat (LS: 1846.8)

Lineup: Kendrick Nunn | Jimmy Butler | Duncan Robinson | Derrick Jones Jr. | Bam Adebayo

Net Rating: Plus-11.4 over 162 minutes

Let's start with everyone's favorite talking point: technicalities! Yes, Bam Adebayo is a center. While he's played more 4 than 5 this season, he has still spent 75 percent of his career minutes at the latter post.

But he also aces the small-ball-big-man boxes for playmaking (5.1 assists, second-most among this season's bigs) and five-position switchability on defense, which makes him an ideal fit as a contemporary center.

"Adebayo has become everything you want a modern center to be," FiveThirtyEight's Jared Dubin wrote. "He is both willing to do the dirty work and capable of doing much more than that. He's a strong screener, passer and finisher, and an incredibly active defender."

This quintet gives Miami three turbo-charged switchers on defense in Adebayo, Jimmy Butler and Derrick Jones Jr. Both Butler and Adebayo can handle primary passing duties, and even if Kendrick Nunn is most comfortable hunting his own shots, he's still a serviceable secondary table-setter.

Duncan Robinson has proved Heat coach Erik Spoelstra prescient for his preseason declaration that Robinson is "one of the best shooters on this planet," per Anthony Chiang of the Miami Herald. Robinson has splashed more catch-and-launch threes than anyone (206), and his 45.8 percent conversion rate is tops among the 17 snipers with 110-plus such makes.

Between Robinson's shooting, Nunn's self-sufficient scoring, Butler's comfort in isolations (68th percentile), Adebayo's explosiveness as a pick-and-roll screener (ninth-most points as a roll man) and Jones' aerial antics, this offense can attack in waves. Since Butler, Adebayo and Jones can handle most defensive assignments, they can cover for the occasional leaks from Nunn and Robinson.

2. Los Angeles Clippers (LS: 2142)

Lineup: Reggie Jackson | Lou Williams | Landry Shamet | JaMychal Green | Montrezl Harrell

Net Rating: Plus-35.7 net rating over 60 minutes

Seeing the Clippers land one of basketball's best small-ball lineups should surprise no one. They have interchangeable All-Star wings in Kawhi Leonard and Paul George, plus a 6'1" point guard who functions like a three-and-D wing in Patrick Beverley.

And yet, none of those three appears on what the stat sheet says—likely in a bit of small-sample size shenanigans—is the Clippers' best undersized quintet. But a five-man lineup featuring Leonard, George, Beverley, Lou Williams and Montrezl Harrell has an even smaller sample (56 minutes) and not nearly the same dominance (plus-14).

Over time—say, as long as it takes Reggie Jackson to remember he's not actually a 52.5/45.2/90.0 shooter as he's been over his first nine games in L.A.—the advantage would surely favor the Clippers' star-studded core. But under our guidelines, the bench brigade gets the nod.

Jackson and Williams serve as co-offensive triggers, and each can create his own scoring chances or sniff them out for teammates. Harrell shines as both a screen-setting bulldozer and a punisher in the post (74th percentile on post-ups). Landry Shamet (39.5 percent) and JaMychal Green (36.6) are sharpshooters off the catch.

Defensively, this group should have more issues than it has encountered. The 6'1" Williams and 6'3" Jackson aren't exactly stone walls in the backcourt, and Shamet lacks both bulk and lateral quickness. But at least Green and Harrell can handle perimeter switches, and since this is a reserve unit, these five have had enough to stifle opposing second teams (88.9 defensive rating).

The eye test may not identify this as the season's second-best small-ball grouping, but numbers never lie.

1. Boston Celtics (LS: 2350)

Lineup: Kemba Walker | Jaylen Brown | Jayson Tatum | Gordon Hayward | Daniel Theis

Net Rating: Plus-12.5 over 188 minutes

So much for the Celtics having a problem at center, right? Sure, the offseason exits of Al Horford and Aron Baynes seemed worrisome, especially when they weren't preceded by Anthony Davis' arrival. But the Celtics trusted what they had, and they've reaped the rewards ever since.

Daniel Theis isn't the typical NBA center at 6'8" and 215 pounds, but that's the point. This entire roster oozes versatility, and the (relatively) little big man enhances it. He can defend in space or at the rim, move the ball (2.5 assists per 36 minutes), dislodge his teammates' defenders (9.7 screen assist points per game, tied for 13th-most) and hit a three if left unattended (36.6 percent on wide-open triples).

"Theis knows how to play at both ends of the court," Celtics skipper Brad Stevens said, per The Athletic's Jay King. "He's really good. The whole thing was, 'How do we accentuate our wings? How do we accentuate Kemba?' And he fits that. He's figured out how to make all those guys better when he's on the court at both ends."

This probably seems like a ton of Theis talk given the caliber of the other players in this lineup, but really, he was the lone wild card. Kemba Walker, Jaylen Brown, Jayson Tatum and Gordon Hayward are all adequate (or, in most cases, better) passers, scorers, shot-creators and shooters. Walker has been a perfect replacement for Kyrie Irving, while Brown, Tatum and Hayward offer enviable interchangeability at the 2 through 4 spots.

Boston's versatility is otherworldly. If we allowed two entries from one team, then the Shamrocks would've claimed the second spot too, as the group with Marcus Smart in Brown's place boasts a lineup score of 2213.9 (plus-13.1 over 169 minutes).

This lineup has four players between 6'6" and 6'8", plus a point guard with slippery handles, shooting range and a mean scoring punch. That sounds an awful lot like a certain Death Lineup that lorded over the Association in recent years, doesn't it?

All stats, unless otherwise noted, courtesy of NBA.com and Basketball Reference.

Zach Buckley covers the NBA for Bleacher Report. Follow him on Twitter, @ZachBuckleyNBA.