Spurs coach Gregg Popovich said Parker, Duncan and Ginobili know that if they stick with what they know works, victories more often than not will come.
"I think they play within the system and trust each other enough it comes out pretty good for them," Popovich said, "most of the time."
Shannon Brown, starting because Grant Hill was a late scratch with right knee inflammation, scored a career-high 32 for Phoenix. Marcin Gortat added 21 points and 14 rebounds in just the second home loss for the Suns in 10 games since the All-Star break. Steve Nash had 16 points and eight assists.
"We got close," Nash said. "We kept ourselves in the game for a long time and couldn't ever really get more than that five- or six-point lead, and they came flying back, and then the start of the fourth there they kind of got up by nine and we couldn't close back the distance."
Brown, who signed with the Suns as a free agent before the season, matched his career best with five 3-pointers, in 10 tries.
"I didn't know I was going to start until we were doing our pregame [meeting] and they said Grant wasn't going to go," Brown said, "so I had to prepare myself mentally. I just wanted to come out, play hard, play within the flow of what's going on, and I wish we could have come out with a win."
Phoenix shot 51.5 percent through three quarters but made just 33 percent (7-of-21) in the fourth.
"Shannon Brown was making crazy shots so we felt like if we could hang in there things were going to turn and they're going to miss at some point," Parker said, "and they started missing, and we played better defense."
The Spurs led by as many as nine in the first half and were up 62-57 at the break behind Duncan's 17 points and eight rebounds. Duncan was 8-of-9 from the field.
Phoenix started the second half with a 12-2 run to go up 69-64 on Gortat's 6-footer. Brown's fifth and final 3-pointer of the night put the Suns ahead 79-74 with 4:50 left in the third quarter, but San Antonio scored the next six, the last four by Ginobili, to take an 80-79 lead. The Spurs were up 84-83 entering the fourth.
After Robin Lopez's reverse layup cut San Antonio's lead to 88-87 with 10:08 to play, Parker started the decisive run with a layup on a pass from Ginobili. Parker followed with a 13-footer, then made a 20-footer. Boris Diaw sank a 20-footer, then Parker capped the outburst with a 10-foot jumper after Phoenix's second straight turnover, and the Spurs led 98-87 with 5:59 to go.
Nash's 18-footer cut it to 98-89, but Leonard made a 3 from the corner to put San Antonio ahead 101-89 with 5:29 to go.
Brown was fouled by Leonard on a 3-point attempt and made all three from the line to slice the lead to 103-94 with 3:15 to go, then Jared Dudley's tip-in, his lone basket of the night, cut it to 103-96 with 1:22 to play. Brown's driving layup made it 103-98, but with just 33.9 seconds left, Phoenix ran out of time.
Parker sealed the victory with four straight from the foul line.
"We let them get a little separation there, and we had a couple crucial turnovers and crucial offensive rebounds," Phoenix coach Alvin Gentry said, "and that's kind of what they do to people."
Phoenix shot 56 percent in the first half, San Antonio 55 percent. ... The teams meet three times in the final 29 days of the season, twice in the final 11. ... Phoenix fell two games behind idle Utah and Denver for the No. 8 playoff spot in the West.