The All-Star forward's return to the team included "verbally challenging teammates, coaches and front office executives" and a scrimmage in which Butler led third-stringers against the team's starters, according to ESPN.
Butler was reportedly vociferous and emotional at times in targeting Tom Thibodeau, Scott Layden, Karl-Anthony Towns and Andrew Wiggins.
As the GM watched on the sidelines during a scrimmage, sources said that Butler yelled to Layden: "You f--ing need me, Scott".
According to an ESPN report, Butler practiced with the Timberwolves on Wednesday.
It was Butler's first appearance at training camp since the 29-year-old Houston native asked for a trade last month.
Outside of the Heat, the Timberwolves have had no serious, active talks ongoing with any other team recently, league sources said.
Jimmy Butler arrived in Minnesota to join the Timberwolves and begin preparations for the regular season today.
When practice concluded, Butler stormed out of the facility and skipped stretching with the rest of his teammates, league sources said. Coaches and players were largely speechless at Butler's tour de force throughout the workout, league sources said. Minnesota and Miami advanced to the brink of a blockbuster trade for Butler over the weekend - only for the deal to fracture before completion, sources told ESPN. He dominated the gym in every way.
Proposed changes from Minnesota created a breakdown in earlier trade negotiations just as the teams were close to finalizing a deal. He would become an unrestricted free agent after this season, and would likely get a five-year maximum contract from interested suitors.
Butler's friend and current Boston Celtics guard Kyrie Irving requested a trade from the Cleveland Cavaliers in 2017 and it took the Cavs six weeks to pull off a deal.