Reserve Patty Mills had 16 points for the Spurs, who scored a season high in points. It’s their longest regular season win streak since reeling off 17 straight from February 29 to March 31, 1996.
San Antonio also maintained a three-game lead for the top playoff seed in the Western Conference.
“This (winning streak) is great challenge,” Duncan said. “It’s a big challenge. People can get lackadaisical and look past certain games. We’ve done a good job of not doing that.”
Randy Foye scored 20 for the injury-depleted Nuggets, who lost for the fourth time in five games.
In other games, Miami’s LeBron James got his first triple-double of the season, with 17 points, 12 assists and 10 rebounds in the Heat’s 110-78 win over the Detroit Pistons.
The banged-up Heat had little trouble with the Pistons even though they were without Dwyane Wade, Mario Chalmers, Ray Allen and Greg Oden. James helped Miami build a big lead, and then rested in the fourth quarter.
Chris Bosh scored 15 for Miami.
The Indiana Pacers, coming off a big win over Miami in a matchup of the top two teams in the Eastern Conference, meanwhile, fell to the Washington Wizards 91-78.
John Wall scored 20 points and Marcin Gortat added 17 points and 12 rebounds for the Wizards, who dropped their first two games against the Pacers this season by a combined 47 points.
Paul George scored 19 points for the Pacers, who have lost a season-high four straight road games.
The Phoenix Suns got their season-high sixth straight victory, trouncing the New York Knicks 112-88, to move a game ahead of idle Dallas for the eighth and final playoff berth in the crowded Western Conference.
Goran Dragic scored 32 points in 32 minutes and Eric Bledsoe added 16 points, seven rebounds and six assists for the Suns.
The Knicks were blown out for the second time on their five-game Western road trip, falling two games behind Atlanta for the eighth spot in the East.
The Toronto Raptors clinched their first playoff berth in six seasons with a 105-103 win over the Boston Celtics, their 18th victory in 24 home games.
DeMar DeRozan scored 30 points for the Atlantic Division-leading Raptors, who last reached the playoffs in 2007-08 and have only made the playoffs six times in 19 seasons.
Minnesota’s Kevin Love got the second triple-double of his career, with 22 points, 10 rebounds and 10 assists in the Timberwolves 143-107 demolition of the Los Angeles Lakers.
Nikola Pekovic scored 26 points on 9-for-10 shooting in his first game back from an ankle injury and Kevin Martin scored 17 points.
Steve Nash made a surprise appearance for the Lakers, picking up four points and six assists in just his 12th game of the season.
The Golden State Warriors beat Memphis 100-93 to move two games ahead of the Grizzlies for the sixth playoff seed in the West.
Stephen Curry scored 33 points, including a tiebreaking 3-pointer, as Golden State used a closing run to beat the Grizzlies, who had won eight of 10.
The Brooklyn Nets beat the Cleveland Cavaliers 108-97 for their 12th straight home victory and the Orlando Magic topped the Charlotte Bobcats 110-105 in overtime.