DENVER — Two and a half years after they hastened the league’s small-ball craze by riding an undersize lineup to the 2015 NBA title, the Warriors face a bit of a conundrum: Why is the group known as the “Hamptons 5” relatively ineffective?

One of the best lineups in NBA history — Stephen Curry, Klay Thompson, Andre Iguodala, Kevin Durant and Draymond Green — has been outscored in its 82 minutes this season. Injuries and periodic rest have made it tricky for that group to settle into a groove, but its issues extend deeper than a lack of time together on the court.

After watching Curry, Thompson, Iguodala, Durant and Green overwhelm opponents to the tune of plus-125 in 224 minutes last season, teams are better versed on how to defend a crew that boasts four All-Stars in their prime and an NBA Finals MVP. It also doesn’t help Golden State that Green and Iguodala are laboring from deep.

Green’s 30.1 percent clip from three-point range is on pace to be his worst since his rookie season. Though still a capable defender and ballhandler, Iguodala is averaging 5.6 points per game on 43.1 percent shooting from the field and 23.4 from three-point range; all of those are career lows. Defenses are free to leave Green and Iguodala unguarded along the perimeter, snuff out Curry and Durant in pick-and-roll situations, and send double teams where necessary.

It all has left head coach Steve Kerr searching for a solution to his spacing problem. With the score tied midway through the fourth quarter Saturday night in Denver, he made a substitution that might have surprised some: Nick Young, a 38.9 percent shooter from three-point range this season, entered for Iguodala.

Less than 24 hours earlier in Sacramento, with Iguodala given the night off to rest, Young had drained two late three-pointers to help Golden State polish off a win. With the game hanging in the balance in Denver, Kerr wanted to see whether Young again could provide a lift down the stretch.

As Iguodala — the fifth member of that Hamptons 5 lineup that typically closes out games — watched from the bench, Young committed a silly foul on Nikola Jokic, who hit both free throws to push the Nuggets’ lead to 109-104. Little more than a minute later, Young air-balled a three-point try and, upset with a no-call, unleashed on referee Ed Malloy, earning a technical foul.

Durant joined in berating Malloy and also was assessed a technical. Denver guard Jamal Murray sealed the Warriors’ fate at the foul line with six free throws, leaving the defending NBA champions to grapple with their second loss in three outings.

“Just felt like we wanted to see what it looked like with another shooter on the floor,” Kerr said of his decision to replace Iguodala with Young late. “Experimenting.”

With the All-Star break 10 days away, Kerr is trying anything that will get his team through its doldrums. Saturday’s loss came on the heels of a 30-point defeat in Utah and a 25-turnover game in Sacramento.

However, this much remains certain: As the Warriors near the playoffs, Kerr will lean heavily on the Hamptons 5 to close out games. Unflattering analytics don’t change the fact that Curry, Thompson, Iguodala, Durant and Green give Golden State as good a chance as any lineup of winning.

“I’m pretty sure you’ll know what the lineup is down the stretch of the season,” Curry said.

Connor Letourneau is a San Francisco Chronicle staff writer. Email: cletourneau@sfchronicle.com Twitter: @Con_Chron