Orlando, which is 3-3 since Nelson’s injury, needed help at the position.

Nelson had the procedure performed Thursday by Dr. James Andrews in Birmingham, Ala. and the Magic said he would need an estimated four to six months of rehabilitation. Alston helps fill the void for the rest of the season.

The 6-foot-2 Alston practiced with the Rockets on Thursday but left before the session was opened to the media. He was averaging 11.5 points this season and had 24 assists in Houston’s last two games, both victories.

Alston was due to make $4.9 million this season and $5.25 million next season, the last year of his contract with Houston. The Rockets acquired him in an October 2005 trade with Toronto.

“What he does is compete,” Magic general manager Otis Smith said of Alston. “What he does is battle every night. What he does is not allow guys to take a step back.”

The move reunites Alston with Coach Stan Van Gundy, who led Miami when Alston played for the Heat in 2003-04. Alston played for Jeff Van Gundy, Stan’s brother, in his first two seasons with the Rockets.

“It’s great to go to a team that wants you,” Alston told Houston television station KRIV. “It’s an honor and privilege to go to a team that is willing to trade something to get you.”

The 6-9 Cook is averaging only 3 points and 1.3 rebounds in 21 games for the Magic this season. Morey acknowledged that Cook may not see much playing time, backing up Luis Scola and Carl Landry, but he may be useful in specific situations.

“He gives us another chess piece,” Morey said. “If we’re playing a team and we want to spread them out, Cook can play (center). It would give them another tool on the roster.”

More on  Rafer Alston | Aaron Brooks

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