Pietrus made two 3s to open the fourth, and Nelson connected with 2:53 left to make it 96-88. Dwight Howard had 22 points, 13 rebounds and six blocks for Orlando.
Delonte West had 21 points, and Mo Williams had 19 points and nine assists for the Cavaliers, who finished the regular season 35-6 at home.
In Los Angeles, Martell Webster hit three free throws with 3.1 seconds left, and Portland tied San Antonio and Oklahoma City for sixth place in the Western Conference to improve its chances of avoiding Los Angeles in the first round of the playoffs.
Kobe Bryant and Derek Fisher combined to miss three free throws in the final 6.9 seconds, and Pau Gasol missed a 3-pointer at the buzzer for the top-seeded Lakers.
LaMarcus Aldridge had 24 points and 11 rebounds for the Blazers, who lost leading scorer Brandon Roy at halftime because of sore right knee.
Gasol led the Lakers with 23 points and 12 rebounds, Lamar Odom added 16 points and 15 rebounds, and Bryant had 20 points on 8-of-23 shooting.
In Toronto, Derrick Rose scored 26 points, Joakim Noah had 18 points, 19 rebounds and seven assists and Chicago beat Toronto to take a one-game lead over the Raptors for the final Eastern Conference playoff spot.
Luol Deng scored 14 points, Taj Gibson had 11 and Ronald Murray and Hakim Warrick each scored 10 points for the Bulls, who led by 25 points.
Chicago has won eight of 12 since Noah returned from a foot injury that forced him to miss 10 games. The Bulls went 0-10 without him.
Sonny Weems and Andrea Bargnani each scored 18 points for the injury-riddled Raptors, who lost their fifth straight. Hedo Turkoglu had a career-high 19 rebounds and nine assists but shot 2 for 12 and scored just six points.
In Phoenix, Amare Stoudemire had 35 points and 13 rebounds and Phoenix used 3-pointers to pull away at the finish.
The Suns made four 3s in a row, two by Channing Frye and one each by Steve Nash and Jason Richardson, in a 14-0 run after Houston took a 102-100 lead with 3:23 left.
Phoenix moved into a tie with Utah and Dallas for the third playoff spot in the West, a half-game behind No. 2 Dallas, with two to play.
Nash had 23 points and 11 assists for the Suns, winners of 12 of their last 14.
Luis Scola scored 20 of his 30 points in the second half for Houston.
In Oakland, Calif., Monta Ellis scored 27 points in his return following a two-week absence, Stephen Curry added 25 and Golden State overcame a 20-point deficit to beat playoff-bound Oklahoma City.
The Warriors missed three free throws in the final 53 seconds but held on to win when Kevin Durant’s 3-point attempt with a second left bounced off the back of the rim.
Durant finished with 40 points for Oklahoma City, which dropped into the eighth seed in the Western Conference with two games remaining. The Thunder are tied for sixth with Portland and San Antonio, but the Blazers and Spurs hold the tiebreakers.
In New York, Dwyane Wade scored 32 points and Miami pulled into a tie for fifth place in the Eastern Conference with Milwaukee.
Michael Beasley added 16 points, and Udonis Haslem and former Knicks forward Quentin Richardson had 14 apiece for the Heat, who won for the 10th time in 11 games.
David Lee scored 26 points for New York.
In New Orleans, Emeka Okafor scored 23 points, Marcus Thornton added 22 and Darren Collison had 17 points and 11 assists to help New Orleans snap a five-game losing streak.
Julian Wright added a season-high 16 points, and David West had 10 points and 12 rebounds in the Hornets’ final home game of the season. Ryan Gomes scored 18 points for Minnesota. The Timberwolves have lost five straight and 21 of their last 22 games.
