San Antonio Spurs forward Tim Duncan (21) shoots over Dallas Mavericks forward Dirk Nowitzki (41) during the second half at the American Airlines Center. The Spurs defeated the Mavericks 109-100.[Photo/Agencies]??

DALLAS -- San Antonio Spurs guard Patty Mills, starting in place of injured Tony Parker, took full advantage of the opportunity with a game-high 26 points and put a dent in the Dallas Mavericks' playoff hopes.

Mills, who made six 3-pointers, scored 11 points in the third quarter as the Spurs outscored the Mavs 34-21 to reclaim the lead. From there, San Antonio closed out an impressive 109-100 victory on Thursday night at the American Airlines Center.

The Spurs (61-18) crept ever closer to clinching the No. 1 seed in the Western Conference. For the Mavs (48-32), the desperation grew just to make the playoffs with two games remaining against the two teams they are battling for the final two playoff spots.

Dallas plays the Phoenix Suns at home on Saturday and the finishes the regular season at the Memphis Grizzlies on Wednesday. The Suns play at San Antonio on Friday night.

Dallas' magic number to clinch a playoff spot remains two -- any combination of Dallas wins and Memphis losses.

Each time Dallas seemed to gain some footing against the Spurs, they got knocked down and then knocked out by a massive 28-6 San Antonio run that bridged the third and fourth quarters. The Spurs built their largest lead at 88-72 with 10:11 to go.

The Mavs made a quick run to cut the deficit to 10, but after a timeout, the Spurs regained a 13-point bulge.

San Antonio got significant contributions from ageless forward Tim Duncan, who had 20 points and 15 rebounds, and forward Kawhi Leonard, who also had a double-double with 16 points and 16 rebounds and added five assists. Center Tiago Splitter finished with 12 points and guard Manu Ginobili had 10.

Dallas forward Dirk Nowitzki, who finished with 19 points, did not get much help early and then managed just two points in the fourth quarter when guard Monta Ellis finally heated up. Ellis scored 11 of his 24 points in the fourth quarter. Forward Shawn Marion had 12 points.

Mavs guard Vince Carter, who has made more 3-pointers than any other player in the league off the bench, did not attempt one all game against the Spurs' tight defense. Dallas was just 5-for-12 from beyond the arc and San Antonio went 16-for-34.

Spurs guard Danny Green set the early tone, knocking down his first three 3-pointers for nine of his 15 points in the first quarter.

The Spurs got an early injury scare when Duncan went down in the first quarter grabbing his right knee. He stayed on the floor before getting up and heading straight to the locker room. To the relief of the Spurs, Duncan returned to the game moments later.

Dallas used a 16-2 run in the opening five minutes of the second quarter to erase a 30-22 deficit but quickly gave it back with an 11-0 Spurs run.

The Mavs still managed to take a 51-49 lead into at halftime but were outscored 6-0 to start the third quarter.