Brown appeared to announce the news himself:
Ian Rapoport of NFL Network reported that the Raiders are dealing a third-rounder and fifth-rounder from the 2019 draft for Brown, who will also receive a "reworked" deal to make him the league's highest-paid wideout.
The Raiders needed a No. 1 wideout after trading Amari Cooper to the Dallas Cowboys in October, and Brown should fill that role easily. He caught 104 passes for 1,297 yards and a career-high 15 touchdowns in 15 games last season.
While the 30-year-old will solidify one position in the Raiders offense, the Silver and Black must solve other questions.
Below you'll find a projected 2019 starting lineup with Brown as the new centerpiece alongside notes on the team's potential future at running back and wide receiver.
Projected 2019 Oakland Raiders Starters (Among Players Under Contract)
QB: Derek Carr
RB: Jalen Richard
WR: Antonio Brown, Jordy Nelson, Seth Roberts
TE: Lee Smith
OL: LT Kolton Miller, LG Kelechi Osemele, C Rodney Hudson, RG Gabe Jackson, RT Donald Penn
Both players are free agents, leaving the Raiders with a murky running back future. Jalen Richard is the team's leading running back currently under contract.
On Thursday, Matt Schneidman of the Mercury News wrote that Lynch "has yet to make public a decision about his future, and Raiders coach Jon Gruden doesn't know whether Lynch will retire or want to return for another season."
Lynch said on Real Time with Bill Maher in January that "if it works out that way, then I will" when responding to a question about whether he would play in 2019:
If Lynch returns, he'll be able to suit up in his hometown one more season before the Raiders leave for Las Vegas in 2020. That could potentially be an incentive for Lynch to return.
Plus, the 32-year-old still has something left in the tank if last year is any indication. Lynch was productive in limited time last year, rushing for 4.2 yards per carry in six games. He notably had 157 yards from scrimmage against the Cleveland Browns.
The (completely speculative) guess here is that Lynch returns for one more year, with Richard acting as the change-of-pace and third-down back.
Even with Brown locking up the No. 1 wideout spot, there is still much unknown about the Raiders' pass-catching core.
The Raiders needed a player like Brown after the team dealt Cooper to the Dallas Cowboys. The pass game struggled even with Cooper in the mix, but Oakland didn't get any better without him. The Raiders averaged just 18.0 points per game in their last 10 contests sans Cooper and 18.1 for the season, or fifth-worst in the NFL.
Jordy Nelson and Seth Roberts are still under contract. Nelson was the de facto No. 1 wideout and had team-leading 63 catches for 738 yards and three touchdowns. Roberts had 45 receptions and 494 yards.
As far as where the Raiders can look to improve the roster from the outside, Michael Gehlken of the Las Vegas Review-Journal reported that "the Raiders are considered likely to make a serious run at Los Angeles Chargers wide receiver Tyrell Williams."
General manager Mike Mayock also made some telling comments about where they are going at the X receiver, where Marcell Ateman played to end the year:
"Typically, in most NFL systems, the 'X' is the bigger wide receiver," Mayock said at the NFL Scouting Combine. "Ateman right now is a guy that we like, but again, at all positions, we think we can get faster, more athletic, and that's what we're going to try to do—not just at 'X' but everywhere throughout our roster."
Williams is 6'4", 205 pounds and ran a 4.42-second 40-yard dash at his Oregon State pro day in 2015, per Eric D. Williams of ESPN.com. He's averaged 16.3 yards per reception for his career. If the Raiders are looking to get younger and more athletic, then Williams makes a lot of sense. The Raiders would also enjoy the benefit of making a division rival weaker in the process.
The team could also look to use a late first-round pick on a wideout, which is a common selection in many mock drafts. Ohio State wideout Parris Campbell is an intriguing fit for Oakland given the team's need for a slot receiver. Lance Zierlein of NFL.com compared Campbell to ex-Seattle Seahawk and Minnesota Viking Percy Harvin. A Brown-Williams-Campbell wideout unit could suddenly become one of the more dangerous aerial attacks in the game.
For now, however, the Brown addition makes the current wideout group much stronger.