Wallace left the Pistons after the 2005-2006 season to sign a big free agent contract with the Bulls. His Chicago career wasn't what everyone expected, which led to his being traded to Cleveland during the '07-'08 season.
The Pistons needed frontcourt help after losing Rasheed Wallace to the Celtics this offseason. The deal is reportedly for the veteran's minimum of $1.3 million.
Is Wallace the same player he was in 2004? No. In fact, he's not even the same player he was a few years ago thanks to injuries. But he can still help defensively.