Dirk Nowitzki scored 17 of his game-high 48 points in the third quarter while setting an NBA record for free-throw shooting as the Dallas Mavericks opened the Western Conference finals with a 121-112 win over the visiting Oklahoma City Thunder on Tuesday night.

Nowitzki was virtually unstoppable, making 12 of 15 shots from the floor while going 24 for 24 from the free-throw stripe. That established a postseason record for most made foul shots without a miss, surpassing Paul Pierce's 21-for-21 performance in 2003.

Jason Terry had 24 points off the bench while J.J. Barea added 21 for the Mavericks.

Kevin Durant had 40 points for the Thunder, who will look to even the best-of-seven series with a victory in Game 2 Thursday night in Dallas.

Nowitzki's big third quarter gave Dallas the edge following a back-and-forth first half. He banked a turnaround jumper to make it 73-62 with 4:50 remaining, then found a wide-open Kidd for a 3-pointer - his only field goal of the night - to extend the lead to 14.

Nowitzki finished 13 for 13 from the foul line in the quarter - tying Michael Jordan's record for most made free throws in a quarter - as Dallas led 90-79 after three.

Barea took over early in the fourth, scoring 12 straight Dallas points as the lead grew to as many as 16 points. The Thunder stormed back to close to within five, but Nowitzki hit his 21st and 22nd free throws with 2:31 remaining before stroking a 15-foot jumper over Serge Ibaka's outstretched arm to put the game away.

Nowitzki and Durant traded baskets in the first half, with neither player missing an attempt until well into the second quarter. A Nowitzki three-point play late in the quarter put Dallas up four, and the Mavericks defense held Oklahoma City without a field goal over the final 4:26 to take a 55-48 lead at the break.