Should Warriors let Harrison Barnes go to Mavs on a max deal?

— -- Editor's note (July 4):  Kevin Durant decided on Monday to join the Golden State Warriors, meaning Golden State will most likely pass on matching Harrison Barnes' deal.

The Golden State Warriors will have a decision to make after the NBA's moratorium period concludes and contracts can officially be signed starting next Thursday. The Dallas Mavericks are reportedly set to offer Warriors forward Harrison Barnes, a restricted free agent, a maximum four-year offer sheet worth an estimated $95 million.

As soon as that offer sheet is signed, Golden State will have three days to decide whether to match the offer.

Should the Warriors keep Barnes, or let him go to Dallas?

Projecting Barnes' value

Barnes has never rated particularly well by the advanced statistics that go into those projections. In fact, last season, Barnes rated right at replacement level by my metric (after posting a career-high 2.6 WARP in 2014-15).

Despite his key role on a 73-win team, Barnes doesn't perform much better in ESPN's real plus-minus (RPM). Last year, his minus-1.3 rating ranked 37th among small forwards.

Given his relatively small role in the Golden State offense -- he finished about 16 percent of Warriors' plays while on the court last season with a shot, trip to the free throw line or a turnover -- Barnes would need to be more efficient to be an above-average scorer. Alas, his .559 true shooting percentage wasn't much better than league average (.541), even though nearly three-quarters of his made field goals were assisted in Golden State's elite offense, according to Basketball-Reference.com.

On the plus side, Barnes is still just 24, so he has a chance to continue developing. But overall, he projects as about a two-win player per season.

Given the estimated cost of $4.5 million per win this summer in free agency, plus the cost of the minimum (about a million), that puts Barnes' value at around $10 million per season over the next three years -- less than half his expected new starting salary of $22 million and change.

Assessing Barnes' value to the Warriors

If you're making the case that Golden State should match Dallas' offer sheet, it doesn't start with Barnes' individual performance.

Instead, it revolves around his starting role on a Warriors team that has experienced unprecedented success over the past two seasons, and perhaps more specifically around his spot in the so-called "Death Lineup" that has been key to Golden State's dominance.

Let's take a look at whether that shows up in the numbers, starting with Barnes alongside the rest of the Warriors' starting five.

Besides Barnes, two other players played at least 100 minutes with Andrew Bogut, Stephen Curry, Draymond Green and Klay Thompson during the 2015-16 regular season: sixth man Andre Iguodala and Brandon Rush, who filled in when Barnes missed 16 games with a sprained ankle. Here's how Golden State performed with each of the three players at small forward.

It's worth noting here that we're working with tiny sample sizes out of necessity. A couple of points per 100 possessions either way is not definitive over so few possessions. Still, Iguodala certainly appears to be the better option at small forward -- part of why Steve Kerr went to that lineup when the Warriors needed to win Games 6 and 7 of the Western Conference finals. And Rush held his own as a replacement.

How about Barnes' role in the Death Lineup? That's a slightly more difficult comparison because Iguodala is already part of the Death Lineup and Rush played few minutes (16 total) with that group when Barnes was on the sidelines. So we can only compare Barnes to the other four members of the Death Lineup playing with traditional centers: Bogut and Festus Ezeli.

Intriguingly, the Warriors were pretty great any time Iguodala played with their three All-Stars, but moving Green to center took things to another level. Barnes' ability to defend bigger opposing power forwards -- for example, Zach Randolph in the 2015 series with the Memphis Grizzlies -- is a key to the Death Lineup and probably his most difficult attribute to replace for Golden State.

While another wing might have been able to do something similar, we don't have statistical evidence for that conclusion.

Should Warriors match? Would Barnes be a good get for the Mavs?

In a vacuum, it's pretty clear that Barnes is not a max-caliber player, something that might matter more to Dallas than to Golden State.

In fact, if Golden State decides not to match the offer sheet, the Mavericks will probably regret paying so much for such a limited player. The Mavs' most recent primary small forward, Chandler Parsons, created far more of his own offense than Barnes, using plays at an above-average rate while getting assisted 60 percent of the time. When Barnes has been given the opportunity to do the same, he has struggled.

The Warriors aren't making their decision in a vacuum, however. Unless Kevin Durant chooses to sign with Golden State, the Warriors probably need to match the Mavs' offer sheet.

Letting Barnes go would mean going under the cap to replace him and giving up Bird and early Bird rights on other free agents. Given that, I think the risk of neutering the Death Lineup is too great; thus, the Warriors should match.

On the plus side, Barnes getting a max offer relatively quickly is a good sign for Golden State's future flexibility. In the event the Warriors want to move his contract to use cap space next summer to obtain another player -- perhaps Durant, if he signs a contract elsewhere that allows him to return to free agency in 2017 -- they can probably do so. If the Mavs (and other teams) value Barnes as a max player, Golden State should be able to offload him down the line without having to give up draft picks.