OKLAHOMA CITY Thunder forward James Harden underwent tests Monday following his concussion in the previous day's game against the Los Angeles Lakers and will be re-evaluated on Tuesday.

Harden participated in limited activities on Monday but must go through additional steps under the NBA's concussion policy before he is cleared to play again.

Harden dropped to the floor after taking a vicious backward elbow to the head from Metta World Peace after the Lakers' forward had dunked over two Thunder players late in the second quarter of Los Angeles' double-overtime win Sunday.

World Peace, who claims he accidentally clipped Harden while celebrating the dunk, faces discipline from the NBA as the regular season winds down and the Lakers prepare to open the playoffs this weekend.

"It was unfortunate that James had to get hit with an unintentional elbow," World Peace said. "I hope he's OK."

In other NBA news:

 * Ernie Grunfeld and the Washington Wizards have agreed to a contract that will keep him as team president, a source confirmed to the Associated Press. Grunfeld joined the Wizards in June 2003.

In games last night * 

At San Antonio, Tim Duncan scored 18 points and the San Antonio Spurs clinched the top playoff spot in the Western Conference and pushed their win streak to eight, beating Portland, 124-89.

* At Milwaukee, the Bucks got 25 points from Brandon Jennings in a 92-86 victory over Toronto, but they were eliminated from the playoff race by the Sixers' victory over New Jersey.

* At Washington, John Wall had 16 points and 14 assists, Nene scored 18 points and Jan Vesely had 16 points on 8-for-8 shooting as the Wizards handed the Charlotte Bobcats their 21st straight loss, 101-73. It gave the Wizards their first four-game winning streak since Dec. 9-13, 2007.

Charlotte forward Tyrus Thomas was ejected for throwing an elbow at Washington's James Singleton late in the first quarter.

* At Indianapolis, Paul George scored 27 points to help the Indiana Pacers beat Detroit, 103-97.

* At Memphis, Marreese Speights had 17 points and 10 rebounds, Marc Gasol also scored 17 points, and the Grizzlies beat Cleveland, 109-101.