The Houston Rockets have asked the NBA for a disabled player salary cap exception in the wake of Yao Ming's season-ending ankle injury.

Yao has been out since November 10, and the team announced last Friday that he had a stress fracture in his left ankle. The seven-time All-Star, who missed all of last season following reconstructive foot surgery, appeared in only five regular-season games this year before going down again.

The disabled player exception would allow the Rockets to acquire a free agent, or trade for a player without having to match salaries, up to the value of the midlevel exception (about US$5.75 million).

Team spokesman Nelson Luis confirmed the Rockets' decision yesterday, a request first reported by the Houston Chronicle. The NBA granted Portland a disabled player exception earlier this month after Greg Oden suffered a season-ending knee injury.

The league granted Houston the same disabled player exception for Yao in 2009, and the Rockets used that money (about US$5.7 million) to sign swingman Trevor Ariza. Houston traded Ariza to New Orleans after one season as part of a four-team deal that brought Courtney Lee to the Rockets.

Houston has gone 8-3 in December to inch closer to 500 after a rocky start. The Rockets play the Los Angeles Clippers today.

The team managed to go 42-40 last season with Yao, the top overall draft pick in 2002. Yao first began to have injury problems in the 2005-06 season, mostly in his left foot.

He played in 77 regular-season games in 2008-09, but then sustained a hairline fracture in his foot that required complex surgery.

The Rockets carefully monitored his minutes coming into this season, but Yao was injured in Houston's 98-91 loss to the Washington Wizards on November 10.

After missing only two games in his first three seasons, Yao sat out 91 over the next four years. He missed only five games in the 2008-09 season, then broke his foot in the playoffs.