Blackburn (4-4) allowed seven hits and struck out six, throwing a career-high 127 pitches for his fifth career complete game and the Twins snapped a nine-game home losing streak.
Doug Fister (2-5) gave up four runs and nine hits with six strikeouts in 6 2-3 innings. He balked home the go-ahead run in the seventh inning and the Mariners saw their season-high six-game winning streak come to an end.
The game turned in the seventh inning when Fister committed a balk while faking a throw to third base. That allowed Rene Rivera to score for a 3-2 lead.
Fister threw his hands up in bewilderment and Mariners manager Eric Wedge hollered at the umpiring crew from the dugout, but replays showed a clear balk and Span followed with an RBI double to make it 4-2. Span had a double and a triple and raised his batting average to .301.
Blackburn's gem couldn't have come at a better time for Minnesota's beleaguered bullpen. Closer Matt Capps and setup man Joe Nathan were both unavailable after throwing on Monday night and right-hander Kevin Slowey was scheduled to be tested for a sports hernia on Wednesday and was not an option.
Olivo's two-run homer in the fourth tied the game, but the Twins defense picked up Blackburn with a couple of stellar plays. Kubel made a brilliant diving catch in right field to end the fourth inning and Casilla charged a grounder to throw out Olivo at home plate and keep the game tied in the seventh.
The Twins were one of the favorites to win the AL Central when the season began. But they have been ravaged by injuries to key players Joe Mauer, Jim Thome and Tsuyoshi Nishioka and plagued by sloppy play in the first two months of the season, a toxic mix that has resulted in the worst record in the majors.
The Mariners know a little something about not meeting expectations. They were expected to contend for the AL West crown last year with a nucleus of Felix Hernandez, Cliff Lee, Chone Figgins and the guidance of aging icon Ken Griffey Jr. But they stumbled badly out of the gates and the season quickly descended into chaos, with Griffey retiring, Lee being traded to Texas and 101 losses.
They lost 11 of their first 15 games this season, but have rebounded of late. They had won seven of their last eight games and entered the game just one victory shy of .500 at 23-24.
But after rallying from a 7-4 deficit to beat the Twins 8-7 in 10 innings in the series opener on Monday night, the Mariners had no answer for Blackburn.
NOTES: Twins RF/2B Michael Cuddyer missed the game with a strained right hip, but said he thought he'd be ready to go for the series finale on Wednesday. ... Mariners manager Eric Wedge gave CF Franklin Gutierrez the night off, but said he would likely be back in the lineup on Wednesday against LHP Brian Duensing. ... Mariners SS Brendan Ryan had three hits, none of which left the infield.
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