DETROIT -- Nick Blackburn's season-long struggles led the Twins to option him to Triple-A Rochester on Wednesday after another poor outing against the Tigers on Tuesday. Right-handed reliever Casey Fien's contract was purchased from Rochester to take Blackburn's place, and he will join the Twins in time for Thursday's game in Detroit.

Blackburn lasted just four innings against the Tigers on Tuesday, allowing six runs on eight hits, including two homers. The right-hander has a 4-5 record and an 8.10 ERA in 13 starts this season.

"There was no final straw," Twins assistant general manager Rob Antony said. "It's just a matter of he was struggling. He wasn't getting it done and he doesn't have confidence -- it doesn't look like he was pitching with confidence -- and we just want him to go down and get himself right."

It's been a tough year for Blackburn, who has thrown just one quality start and hasn't gone longer than six innings in any of his outings. He's also battled injuries, as he missed time with tightness in his shoulder in April and was placed on the disabled list with a strained left quad in mid-May.

"It's been tough the whole time," Blackburn said. "It's very frustrating to go out there and not feel effective. It's been a tough couple weeks. Actually, a tough season. Early on, I felt like I was getting tough breaks and that my pitches were good, but after a while, you start to realize that's not really the case. So to go get some confidence back will be key for me."

It's been a continuation of last year, as the sinkerballer has a 7.61 ERA over his last 24 starts dating back to June 27, 2011. Blackburn pitched well early last year -- he had a 3.15 ERA through his first 15 starts -- but his 7.61 ERA since then is the highest among Major League starters.

Blackburn, who signed a four-year, $14-million extension before the 2010 season, has a career 4.79 ERA in 139 games, 131 starts, over six seasons.

Fien, meanwhile, had a 4.30 ERA with 42 strikeouts and 14 walks in 46 innings with Rochester. He has some big league experience, posting an 8.36 ERA in 14 innings over parts of two seasons with Detroit from 2009-10.

"Casey's been throwing very well," Twins manager Ron Gardenhire said. "Today's report said he's pitching as good as they've seen him throw the baseball. His fastball's 91, 92, 93 mph, and he's a competitor. He can field his position; he's very active, very athletic. So hopefully he'll be able to give us some innings."

Twins discussing options for starter on Saturday

DETROIT -- With right-hander Nick Blackburn being optioned to Triple-A Rochester on Wednesday, the Twins need a starter against the Rangers this weekend, but they've yet to make a decision on who will take the mound at the Ballpark in Arlington.

Blackburn was scheduled to start on Sunday, but the Twins actually need a starter for Saturday, as right-hander Cole De Vries pitched two innings in relief in Wednesday's 5-1 loss to the Tigers.

De Vries was slated to start Saturday but will be pushed back to Sunday, so the Twins still have to decide on a starter for Saturday.

The Twins could opt to go with an internal candidate such as right-hander Anthony Swarzak or could call up a pitcher such as Rochester right-hander Sam Deduno. Or they could go with a bullpen day using multiple relievers because it's right before the All-Star break.

"We'll just wait 'till we get through the next couple of days and we'll make a decision," Twins manager Ron Gardenhire said. "We'll have somebody in place for you."

Gardenhire met with assistant general manager Rob Antony before Wednesday's game to discuss their options, but a decision isn't expected to be announced until this weekend.

"We'll just get through these next few days and figure it out," Antony said. "So we'll discuss that, we'll see if there's any internal bullpen guys, if we want to use one of them for a spot start, or if he wants to do something else."

All-Star Mauer swinging a hot bat

DETROIT -- With three more hits against the Tigers on Tuesday, Twins catcher Joe Mauer raised his average above .330 for the first time this season.

Mauer, who ranks third in the American League with a .332 batting average, leads the AL with a .420 on-base percentage entering Wednesday's game.

He's been on fire recently, as he carries a 12-game hitting streak into Wednesday's game and is hitting .427 in 22 games since June 2.

But Mauer, who was named an All-Star for the fifth time in his career, said he's not quite ready to think about winning a fourth batting title.

"It's funny every year -- I've won three batting titles -- and this is kind of the time of year where it starts to pick up the talk about that," Mauer said. "But I've never really paid too much attention to that or my average or where other guys' average is at. It's more of a mid-to-late September deal. But yeah, I'm swinging the bat well and hopefully I'll continue to do that."