Parker scored 25 points and Duncan had 16 points and 13 rebounds, and San Antonio never trailed, cruising past the Dallas Mavericks 112-90 on Wednesday night.
Both teams were on the second night of a back-to-back, with San Antonio winning in overtime at Memphis and the Mavericks topping the Los Angeles Lakers in Dallas.
Parker got off to a hot start despite playing 40 minutes Tuesday night, and finished 10 for 15 from the field with seven assists in 29 minutes.
"When I woke up this morning, obviously everything hurts and you feel like you're 45 years old and think about 'Man, I should not play in the summer,' " Parker said. "But it worked out. We played great. We had good energy."
The Spurs turned to Marco Belinelli with super sub Manu Ginobili unable to play after straining his left hamstring against the Grizzlies. After starting 11 consecutive games, Belinelli had 17 points, going 3 for 5 on 3-pointers as a reserve.
"[Boris] did all the little things out there and did an excellent job on Dirk," Duncan said. "He gave us a chance to get some space in the game and control Dirk without having to double team him and that was a big advantage for us."
Duncan also provided a huge lift, going 5 for 8 from the field and picking up 10 defensive rebounds and blocking two shots.
He also helped lift his teammates' spirits. From encouraging and joking with teammates during timeouts to teasing the Spurs commentators, Duncan was in high spirits and it reflected in the team's energy.
The Spurs outrebounded the Mavericks 55-32.
"The rebounding killed us all night long," Dallas coach Rick Carlisle said. "We were down 36-18 at halftime and that's just not good enough."
Duncan grabbed five rebounds and Leonard had four in the first 7 minutes of the game, as San Antonio took advantage of Dallas' undersized lineup. Duncan, Leonard and Boris Diaw had 11 points and 12 rebounds to open the game.
The lack of rebounding was made worse by the Mavericks' woeful shooting. They were 6 for 24 in the first 10 minutes while falling behind 23-12.
With Shawn Marion missing the game due to a bruised right shoulder he hurt against the Lakers, Parker had a series of jumpers over Wayne Ellington to open the second half. He scored eight of the Spurs' 10 points as they took a 55-42 lead 3 minutes into the third quarter.
"He made a bunch of shots," Carlisle said. "He really diced up whoever was guarding him. Our team didn't do a good job. The third quarter was a demolition."
Belinelli had five consecutive points, including his first 3-pointer, in putting San Antonio up 76-59 with 1:20 left in the third quarter. He missed a free throw following the 3 after being fouled by Carter.
He scored seven consecutive points to give San Antonio a 93-68 lead with 8 minutes remaining.
"I was happy to sit in the fourth quarter tonight," Parker said. "Especially after last night, playing 40 minutes; it was a long time. So I was happy this time."
Ginobili was a late scratch, missing his second game of the season, but first due to injury. ... Spurs television analyst Sean Elliott fell off his stool after Duncan playfully gave him a two-handed slap in the back during pregame warm-ups. Elliott, preparing for the team's local pre-game show, groaned loudly and laughed as Duncan sprinted off smiling as he tossed in a layup. Duncan returned to torment his former teammate during a timeout, crumpling and tossing Elliott's notes and water bottle at him. ... Former San Antonio center DeJuan Blair received mostly boos when he was introduced in Dallas' starting lineup, but there was a smattering of applause.