After a slow start to their title defense, the reigning NBA champions Dallas Mavericks returned to form to hand the last unbeaten team on the season their first blemish, as the Mavs defeated the Oklahoma City Thunder, 100-87, on Monday.

The Thunder, who lost to the Mavericks in the Western Conference finals last season, gave Dallas their third loss on the season last week when Kevin Durant hit the game-winning 3-pointer at the buzzer. The Mavs entered Monday’s contest at 1-4, looking to redeem themselves against the undefeated Thunder at 5-0. Playing in their fourth game in five nights, Dirk Nowitzki and the aging Mavs put on a shooting clinic and capitalized off Durant and the youthful Thunder’s miscues.

According to ESPN Stats & Information, the Thunder entered the night yielding just 40.6 percent shooting. But for the first time this season, OKC allowed a team to shoot above 45 percent. The Mavs converted 48.8 percent of their shots as they had little trouble finding open shooters and driving lanes to the basket.

From the tip-off at American Airlines Center, OKC had plenty of opportunities to take a commanding lead, when Dallas missed nine of their first 11 shots from the field. But the Thunder didn’t sustain any energy on both sides of the ball, as they gave up 34 points in the second quarter then scored just 18 points in the third. The Mavericks began to pull away at the start of the second quarter, going on a 9-2 run, grabbing nine offensive rebounds that were turned into 10 second-chance points. The Mavs double-digit lead was cut into before the half after OKC forward James Harden hit a 3-point buzzer-beater, for the Thunder to trial by seven, 54-47.

Nowitzki, who scored his 8,000th career basket on a 10-foot, step-back jumper at 7:40 mark in the period, took over in the second-half. The Finals MVP scored 10 of his 26 points during a third-quarter surge; that began when he knocked down a jumper over OKC center Kendrick Perkins, and then converted a shot over Harden, before he scooped in a layup that put Dallas ahead by 15 points, as OKC weren’t able to recover. Nowitzki finished 10-of-16, with six rebounds, three assists and two steals. He moved to fourth among active players in scoring -behind Kobe Bryant, Kevin Garnett and Tim Duncan- and is 31st on the NBA career list.

Dallas’ bench outscored Oklahoma City’s 47-25 and turned the tide with a 34-27 second period. Jason Terry finished with 15 points, Vince Carter had a season-high 14 points and reserve center Ian Mahinmi scored 10 points with nine rebounds. Lamar Odom, newly acquired from the Lakers, has struggled with his new team as he finished with eight points and five rebounds. Shawn Marion scored 17 points and Jason Kidd didn’t score but had a season-high nine assists to round out Dallas starters.

KD and Russell Westbrook couldn’t keep up, as the kids got schooled by the savvy Mavs veterans. Durant led all scorers with 27 points but had just two rebounds and didn’t register a single assist, while turning the ball over three times. Westbrook finished with 18 points but went 8-for-20 from the field and Harden added 16 points and seven rebounds. The All-Star duo combined for just 11 foul shots and the Thunder overall shot poorly at 40.3 percent and had 12 assists against their 14 turnovers.

OKC, now 5-1, will look to start a new streak against the Portland Trailblazers on Tuesday at Chesapeake Energy Arena. The defending champs (2-4) will host Steve Nash and the Phoenix Suns on Wednesday as they continue to come together and improve on the season.