ARLINGTON -- Right-hander Nick Blackburn, who was optioned to Triple-A Rochester on Wednesday, turned in a strong outing in his first start with the Red Wings on Sunday.

Blackburn tossed eight scoreless innings, allowing nine hits without a walk and striking out two. It was a good first step for Blackburn, who had an 8.10 ERA in 13 starts with the Twins before being sent down.

"He chewed them up," Twins manager Ron Gardenhire said. "We need to see Blackie do that again and locate the ball. The big difference with Blackie is he's done it here. We know he can do it. It's about getting him confidence."

The Twins also want Blackburn to continue working on his sinker, as he had problems serving up homers with 15 allowed in his 13 starts.

"The problem with Blackie is he's been hurt by the long ball, which means his ball is flat," Gardenhire said. "If you give up a couple hits as a sinkerballer is one thing, but to misfire and give up a three-run homer is another thing. That's kind of what he was doing up here."

Liriano leads off second-half rotation

ARLINGTON -- The Twins announced their rotation for their first series after the All-Star break, as left-hander Francisco Liriano will start the first game of the second half on Friday against the A's at Target Field.

Fellow left-hander Brian Duensing will start on Sunday, but Saturday's starter is still to be determined. It's expected to be either right-hander Cole De Vries or right-hander Sam Deduno.

"We'll figure out the rotation," Twins manager Ron Gardenhire said. "We'll slot them down the road."

Left-hander Scott Diamond is likely to start the fourth game after the break against the Orioles on Monday. The Twins are trying to give Diamond, who started Thursday, a bit of a break because he's already logged a combined 113 2/3 innings in Triple-A and with the Twins.

"He's thrown a lot of innings so we'll give him that extra break," Twins assistant general manager Rob Antony said. "Somebody is going to go 10-12 days in between starts so I think they believe it can be a benefit to him and won't hurt him."

Walters experiences minor discomfort in shoulder

ARLINGTON -- Right-hander P.J. Walters experienced a minor setback after making a rehab start with Triple-A Rochester on Friday.

Walters, who was placed on the disabled list with right shoulder inflammation on June 14, felt some discomfort in his shoulder on Sunday but it's not considered serious.

He's expected to make another rehab start on Thursday after tossing five scoreless innings on Friday in his second rehab outing.

Walters is also scheduled to fly to the Twin Cities this week to meet with team trainer Tony Leo for precautionary reasons before heading back to Rochester.

"The plan is hopefully he'll be ready to pitch again Thursday down in Rochester," assistant general manager Rob Antony said. "He felt fine after throwing but today it felt like less than a bee sting. He just felt something. I don't think they're too concerned about it. He's coming to Minnesota over the break to see Tony and can see our doctors if need be. But we're not too concerned about it. But it would be good to get him one more before he gets rolling again."