Walters, 28, fared well in nine starts with Rochester, posting a 3.31 ERA with 46 strikeouts and 16 walks in 54 1/3 innings. Walters, who had a 5.69 ERA in 12 starts with the Twins last year, also turned in six straight quality starts for the Red Wings.
"He's been throwing well," Twins manager Ron Gardenhire said. "He's able to control the baseball. He has a nice breaking ball and can add and subtract with all of his pitches. So that's the plus side even though we know he's not overpowering. He can locate and change speeds."
Benson, meanwhile, struggled in Rochester, hitting just .192/.256/.285 with one homer and nine RBIs in 42 games. It was a continuation of last year's struggles for the organization's former No. 5 prospect, as he hit a combined .202 with six homers and 36 RBIs in 76 games split between four levels because of wrist and knee injuries.
It caused his stock to plummet, as 27 teams passed on the chance to claim Benson for $20,000, with the Rangers having the second-best record in the Majors.
"He's done some good things, and we expected big things from him, but he's just struggled the last couple of years," Twins assistant general manager Rob Antony said. "Maybe a change of scenery would be good for him."
Benson, 25, was the organization's Minor League Player of the Year in '10 and got his first taste of the Majors as a September callup in '11, batting .239 with six doubles and a triple in 21 games. But he has hit just .187 in 70 games in Triple-A over the last two years.
"We've been waiting on that fifth tool," Antony said. "He's a pretty good player as he showed a few years ago. Got a taste in September and hasn't been able to [get back]. He came into Spring Training competing for the center field job, and he didn't get it and went down and has been scuffling a little bit. Maybe it's just the right thing and the right time for him."
Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, and follow him on Twitter @RhettBollinger. This story was not subject to the approval of Major League Baseball or its clubs.