Texas made the move before Friday's series opener against Houston, two days after Dyson gave up two home runs and three runs in the 10th inning of a loss to Tampa Bay. It was the sixth loss of the season for Dyson. The right-hander was removed from the closer role in early May, and has blown all four of his save chances this season.
"Just hasn't been able to kind of get back to where he's capable of," general manager Jon Daniels said. "Disappointment on that level that we couldn't do that. At the same time, you just can't hide that on a competitive club very long."
The Rangers reinstated reliever Jose Leclerc from the disabled list. He missed three weeks with a bruised finger. Hard-throwing Matt Bush is now the Rangers closer, with six saves and a 1.37 ERA in 20 appearances. Bush did have a blown save after giving up a tying homer in the ninth inning against the Rays on Wednesday night.
Dyson had 38 saves last season when Texas won its second consecutive AL West title. He was then a key reliever for Team USA when it won the World Baseball Classic in March, but is 1-6 with a 10.80 ERA in 17 appearances for the Rangers this season.
Daniels anticipates being able to work out a deal to trade Dyson, but said there wasn't anything pending yet. Texas has 10 days to trade, release or outright Dyson to the minors, though he could refuse an assignment to the minors and become a free agent if he clears waivers.
The Rangers informed Dyson of their decision after Wednesday night's loss to the Rays. His locker had been cleared out before Friday's game, the opener of a three-game series against the AL West-leading Astros, who are 12 games ahead in the division.
"Less than two months ago, he's mowing through All-Star lineups -- Puerto Rico, Dominican and Venezuela -- at the WBC," Daniels said. "I expect he's going to help somebody else. Wish we would have been able to help him figure it out sooner so that it could have been us. It's not, so we made the decision to move on."
While Dyson's velocity has still been in the mid-90s this season, there have been apparent struggles in getting the sinking movement that helped him succeed.
Daniels said the pitcher is healthy. And when Dyson struck out three in 1 2/3 innings at Detroit less than two weeks ago, Daniels thought the pitcher might have crossed a hurdle.
The Rangers acquired Dyson at the non-waiver trade deadline in 2015, getting him from the Miami Marlins for two minor league prospects.
Dyson took over as the Rangers closer early in the 2016 season when Shawn Tolleson, who had 35 saves in 2015, struggled early. Tolleson had taken over as the closer in the first part of 2015 after Neftali Feliz faltered in that role.