San Antonio shot 72 percent in the first quarter, pounding the ball inside for layups and kick outs to open shooters in taking a 10-point lead.
Duncan battered Andrew Bogut early, making San Antonio's first three baskets on a drive and a jumper over the Australian and on a layup against Landry off a hard pick by Tiago Splitter.
San Antonio went on a 15-0 run on a series of drives to the basket and low-post moves, taking a 27-15 lead.
Curry and Thompson were held to a combined four points on 2-for-10 shooting in the opening 16 minutes, but Barnes had 13 points and Jack seven.
"We just missed shots," Curry said. "Early in the game I got a little off balance a couple (times) trying to get a foul. They play good defense. We didn't get into a rhythm. We just missed shots."
Curry did not make his first 3 until there were 2 minutes left in the first half.
The Spurs stopped going inside in the second quarter, helping Golden State rally.
The Spurs returned to attacking the basket in the third, resulting in another double-digit lead.
NOTES: Duncan surpassed Shaquille O'Neal and tied Wilt Chamberlain for second on the career postseason list in double-doubles with his 143rd. Magic Johnson heads the list with 157 during his Hall of Fame career with the Los Angeles Lakers. . Parker passed Chauncey Billups for fourth in postseason assists among active players with 832. New York's Jason Kidd (1,258), the Lakers' Steve Nash (1,061) and Boston's Rajon Rondo (845) are ahead of Parker. . Richard Jefferson, who played with San Antonio from 2010-2011, continues to receive a chorus of boos from the Spurs' fans whenever he enters the game or makes a shot.