The Timberwolves were warned beforehand by Butler that the situation could get uglier if he wasn't traded before the season, league sources said.
For weeks, Butler has been advocating for a trade that would send him away from Minnesota.
Butler reportedly took part in drills and also scrimmaged with the Wolves.
The Timberwolves open the regular season October 17 at San Antonio.
Butler naturally wasn't in the best of shape, but he held his own, league sources said.
When practice concluded, Butler stormed out of the facility and skipped stretching with the rest of his teammates, league sources said. Timberwolves owner Glen Taylor took a different stance and told owners owners at the National Basketball Association board of governors meetings that "Butler is available, and prospective suitors should contact Taylor himself", according to Wojnarowski.
Minnesota's star swingman, who has been at odds with the organization for almost a month, requested a trade from the Timberwolves on September 19.
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With that in mind, the Heat appear to still be in pursuit.
Butler was vociferous and emotional at times, targeting president/coach Tom Thibodeau, general manager Scott Layden and teammates Karl-Anthony Towns and Andrew Wiggins, league sources said.
Despite his owner's intent to deal Butler, Thibodeau wasn't done trying to keep his star shooting guard.
When reporters were allowed in at the conclusion of practice, Butler wasn't on the court.
Minnesota and Miami were in the "11th hour" of trade talks, according to Wojnarowski, but the deal fell apart as the Timberwolves "pushed late for a sweeter return" in a potential trade.
While these rumors sound fantastic for the Timberwolves moving forward, a trade with the Miami Heat and Houston Rockets now seems (close to) void. "I'm just focusing right now on whoever is here because you have to understand we have a strong group of guys that come in here, put a lot of time and work in".