There's no such thing as certainty when it comes to NBA free agency, but some players are bigger enigmas than others.

Unsettled markets, questionable past production and wide spectrums of future value make a handful of free agents particularly interesting. There's always an element of guesswork involved in concocting offers, but these guys come with especially tricky variables.

When you also consider the possibilities that come with upward of $474 million in cap space across the league (nearly as much as there was in the spendthrift summer of 2016), it gets even harder to set a market value for players with key question marks attached.

We'll leave the higher-end superstars alone in this exercise. Situations can only be so enigmatic when the decision is between max annual salaries for one, four or five years. Instead, we'll zero in on the players a tier or two below.

That's where the intrigue is deepest.

DeMarcus Cousins, Unrestricted

The uncertainty surrounding DeMarcus Cousins is threefold.

First, interested teams will have to make a determination about his health. He finished the 2019 playoffs in the Golden State Warriors' rotation, but that was largely by default as injuries decimated the roster. Coming off a ruptured Achilles and a torn quadriceps muscle, Cousins might have a hard time avoiding injury as he enters his age-29 season.

If teams are satisfied with Cousins' physical outlook, they'll have to decide whether his pre-injury productivity is ever coming back. The big man was never a high flyer, but he was particularly ground-bound in Golden State. Though he's still among the most physically powerful forces in the league, Cousins' lack of lift and lateral mobility made him an even bigger target than usual on defense.

Was his diminished athleticism temporary, the natural result of an Achilles recovery? Or does it portend reduced effectiveness going forward?

It seems safe to assume Cousins won't match his career averages of 21.2 points, 10.9 rebounds and 3.2 assists in any season from here on out, but what level of production should teams expect? And how do they attach a price to such an unknown?

Finally, there's Cousins' long history as a moody, distracting presence on the floor and in the locker room. Are those days behind him after he spent a year occupying a minor role with a title contender? Or will he pick right back up complaining to officials and throwing tantrums in a new locale?

If there were a way to guarantee Cousins' health, production and attitude, he might be in line for max money. But how does a team establish a price when it can't be sure about any of those variables?

Signing Cousins could pay off, but it will require a leap of faith on more than one account.

D'Angelo Russell, Restricted

If teams could be sure D'Angelo Russell will keep shooting the ball like he did in 2018-19, there'd be less mystery here.

Yes, Russell's defense (which graded out as negatively impactful by both ESPN's Real Plus-Minus and Jacob Goldstein's Player Impact Plus-Minus this past season) would remain suspect. And yes, his inability to finish at the rim or draw shooting fouls would still limit his ceiling as a first option.

But if his mid-rangers keep falling like they did last year, when his accuracy rate from that range ranked in the 84th percentile, Russell will continue to be a dangerous pick-and-roll operator who can punish defenses by hitting the in-between shots most willingly concede.

That guy, limitations and all, was an All-Star. He was also one of only 14 players this past season to average at least 20 points and five assists with an effective field-goal percentage north of 50 percent.

At the same time, the Brooklyn Nets' net rating was plus-0.2 points per 100 possessions whether Russell was on the floor or not. So, by one admittedly noisy metric, last year's version of Russell didn't have the kind of impact on winning you'd want from a potential $100 million player.

That's to say nothing of his postseason flop, during which he shot 35.9 percent from the field as switching defenses exposed his lack of one-on-one burst.

Russell's willingness to take big shots at the end of games matters. A player with his confidence has a sustaining effect on the rest of the roster. Teammates can feed off bravado, and Russell has enough to keep everyone around him from going hungry.

But will that self-assuredness play as positively if Russell's shots fall at career-average rates instead of at the marks he set last season? And if last year was an anomaly, will he even grade out as a quality starter going forward considering what he takes off the table defensively?

Russell could be an All-Star several more times or settle into a high-volume, low-efficiency career that more closely resembles what he did during his first three seasons. Even if it's probably smart to trust in the 23-year-old to keep improving, that's a wide range of possibilities, especially for a player some teams may view as a cornerstone.

Malcolm Brogdon, Restricted

For entirely different reasons than Russell, fellow restricted free agent Malcolm Brogdon's future is similarly complex.

Brogdon seems certain to command an offer sheet with an average annual value approaching $20 million. The Milwaukee Bucks are gearing up to match a figure in that neighborhood, according to ESPN's Adrian Wojnarowski. On Wednesday, ESPN's Bobby Marks suggested the Chicago Bulls may be among the teams to come in at that price range.

Are we sure Brogdon's worth it?

You'd be hard-pressed to find Brogdon detractors among the analytically inclined. He posted a 50/40/90 shooting split last year, and he's one of only two qualified players (Kyrie Irving is the other) to shoot at least 48 percent from the field, 40 percent from deep and 89 percent from the foul line over the last three seasons combined.

However, Brogdon is also already entering his age-27 season and has missed 52 games over the last two years. Considering he was medically red-flagged in the 2016 draft because of possible lingering issues in his surgically repaired left foot, maybe the torn plantar fascia in his right foot last year and his partially torn quad tendon in 2017-18 shouldn't be cause for extra concern. The left foot has held up so far.

But at least some worry about his durability seems reasonable.

More broadly, it's fascinating that a player who no one views as a star seems ticketed for such a huge paycheck. Though Brogdon's efficient shooting and reliability on defense (Milwaukee turned to him as Kawhi Leonard's primary defender when it got desperate late in the Eastern Conference Finals) mean he'll have a positive impact on winning, he isn't the kind of player historically rewarded like a 20-point scorer.

Maybe his robust market is a symptom of so many teams being awash in cash this summer, or maybe the league is getting smarter about valuing the right things, whether those things are flashy or not.

Or perhaps free-agent suitors are outsmarting themselves by placing too high of a price on a role player.

Throw in the added intrigue of his irreplaceability on Milwaukee's win-now roster, and Brogdon appears primed for a volatile, unpredictable summer.

Julius Randle, Unrestricted

Julius Randle only has to secure a new deal in the neighborhood of the non-taxpayer mid-level exception (starting at roughly $9.25 million) to justify declining his $9 million player option with the New Orleans Pelicans in 2019-20.

That shouldn't be a problem for a 24-year-old big man coming off a career season during which he averaged 21.4 points, 8.7 rebounds and 3.1 assists.

The potential for Randle to make substantially more than the non-taxpayer MLE is what makes his free agency so interesting.

Randle put up big numbers on a lottery team last year, exhibiting tunnel vision with the ball in his hands and apparently not saving enough energy to play consistent defense. There's little doubt he could reproduce his counting numbers in another low-stakes situation, but it's an open question whether his game will translate on a winning team.

The New York Knicks are interested, according to Marc J. Spears of The Undefeated, and you have to wonder whether they'd lavish a huge contract on Randle if their grander free-agency plans fall through. He projects as a similar fallback option for several other teams who might talk themselves into Randle's numbers.

To the five-year vet's credit, Randle developed a threatening three-point shot last season. If he can duplicate or improve on his 34.4 percent hit rate going forward, he could be a decent value at up to $15 million per season.

Good luck to any team trying to figure out how much Randle's evolving game, inflated 2018-19 production and high-usage approach will be worth on a new deal.

Terry Rozier, Restricted

The 2018 edition of Terry Rozier should be miffed at the 2019 version. The latter may have cost the former significant cash by following up a breakthrough playoff performance with a dud of a regular season.

Rozier stepped in for the injured Kyrie Irving to help lead the 2018 Celtics within a single game of the NBA Finals. Flashing full-time starter potential throughout that postseason, Rozier shone brightest in dispatching the Philadelphia 76ers, averaging 19.0 points, 7.2 rebounds and 4.4 assists while shooting 41.5 percent from deep in a 4-1 conference semifinals win.

In the wake of that effort, it made sense for Rozier to turn down an October extension offer that worth around $12 million per season, according to NBC Sports Boston's A. Sherrod Blakely.

Now, after efficiency declines across the board and some offseason blame-shifting, Rozier might not be in position to do better than the extension he declined.

Was Rozier's progress knocked off course by Boston's rocky season, or did expectations spin out of control after a small-sample postseason anomaly? Is he a high-energy starter or a low-efficiency backup? He's been both within the last 14 months.

Whoever signs him to an offer sheet will have to figure out which one he'll be from now on.

The grapes may be sour enough between Rozier and the Celtics to preclude the team from matching a market-value offer, but Boston isn't swimming in guard depth. If Rozier doesn't attract a hefty offer sheet, the Celtics may decide to keep him and hope next year's refreshed personnel mix draws out more of that 2018 postseason magic.

Stats courtesy of Basketball Reference, NBA.com and Cleaning the Glass unless otherwise indicated. Salary information courtesy of Basketball Reference and Spotrac.com.