"Chi- Town its been real. I appreciate you all. No love lost enjoyed my time in the windy city. Close one chapter open up another," Watson tweeted.
The Chicago Tribune first reported the Bulls told Watson he would not be coming back.
The Bulls must still decide whether to pick up Kyle Korver's $5 million option and whether to match the Houston Rockets' three-year, $25.1 million offer to Omer Asik. The Bulls have not yet received Asik's offer sheet, according to a source familiar with the situation, and they'll have three days to match once the offer is signed.
Brewer became expendable and expensive with 2011 draft pick Jimmy Butler in line for more playing time.
The 6-foot-7 Brewer started 43 games for the Bulls last season as Rip Hamilton battled injuries. Brewer averaged 6.9 points, 2.1 assists and 3.5 rebounds.
"You take the good with the bad," Brewer recently told "The Waddle & Silvy Show" on ESPN 1000. "I liked the situation I was in with the Bulls. I feel like we have a great team. The chemistry was bar none compared to the other teams I've been on. We've had a lot of success, we've won a lot of games in the regular season and had some kind of success in the playoffs."
Watson had a $3.2 million team option for next season and seemed to be a valuable asset to the Bulls, who will be without Derrick Rose for much of next season as he recovers from ACL surgery. But the addition of Kirk Hinrich and the drafting of Marquis Teague priced out Watson.