Bob Nightengale of USA Today added that the Tigers will pick up the majority of Upton's remaining 2017 salary.
Morosi reported Upton informed the Tigers he was likely to opt out after this season given the team's rebuild, which escalated trade talks.
Upton previously cleared revocable trade waivers, making him eligible to get dealt after the July 31 non-waiver trade deadline.
Upton has posted a .279/.362/.542 triple-slash line with 28 home runs, 94 RBI and 10 stolen bases in 125 games with the Tigers this season.
Despite that success and his strong track record from prior stints with the Arizona Diamondbacks, Atlanta Braves and San Diego Padres, the 30-year-old slugger is on the move again. It will be his fifth team in 11 professional seasons.
It's rare for a player who's put up consistently good numbers—Upton ranks in the top 40 among active position players in Wins Above Replacement, per Baseball Reference—to move around so much. It's even more odd when you consider he was the first overall pick in the 2005 MLB draft.
Those are the types of assets teams usually hold on to for as long as possible. But Upton has jumped from franchise to franchise since his time in Arizona ended after the 2012 season.
That seems to have impacted his mindset about trades. George Sipple of the Detroit Free Press passed along comments the outfielder made in late July when asked whether he thought starting pitcher Justin Verlander had made his last start with the Tigers amid heavy speculation.
"That's out of my hands," Upton said. "If it is, it is. This is baseball. Do I think so? I don't know, honestly. Anything can happen. This game's crazy, man. If I were a GM, I'd have a better feel for it. But I don't."
Upton's future is still a key question mark following his latest change of address. Spotrac notes the four-time All-Star holds an out clause in his contract after the season. He can opt for free agency or pick up the last four years of the deal worth $88.5 million.
Ultimately, the decision made by the two-time Silver Slugger Award winner concerning his contract will play a key role in determining the long-term success of the trade. He may fill a corner outfield spot for the Angels for the foreseeable future.
Upton does have a tendency for streaky play—his power surge in August, with 11 home runs in 27 games, is the latest example—but his overall numbers at season's end rarely disappoint. L.A. will hope he can provide a boost down the stretch and, if the option is exercised, into the future as well.
Upton gives the Angels another middle-of-the-order bat who should help immensely in terms of protecting both Mike Trout and Albert Pujols.