Thompson signed a three-year deal reportedly worth around $4 million, as he became the team's first unrestricted free agent signing from another club.
Similar in stature and style to Gadsden, Thompson joins the Dolphins after one breakout season with Washington, during which he caught 53 passes for 773 yards and four touchdowns.
Thompson also had received offers from Minnesota and Philadelphia, and the Dolphins felt they couldn't afford to wait too long without risking losing Thompson.
So after contract negotiations with Gadsden went nowhere, they pulled the trigger on Thompson.
"It was a situation where we were getting pushed into having to make a move," said Rick Spielman, the Dolphins' senior vice president-football operations/player personnel. "We were excited about Oronde and we were excited about this young guy. We weren't going to lose both.
"We felt that with Derrius' timetable and with Philly and Minnesota squeezing, we wanted to try to make one last effort with Oronde to see if we could get close. We weren't able to get close. We were with Derrius and went ahead and made the deal."
Spielman said the Dolphins still want Gadsden back, but it's not looking like that's going to happen.
With top free agent wideouts David Boston, Ike Hilliard and Thompson now off the market, Gadsden might become a more attractive option for teams.
Don't be shocked if he winds up playing for an AFC East opponent, with both the Jets and Buffalo in search of a tall possession receiver.