Twins righthander Nick Blackburn couldn't wait for the regular season to begin. He worked on mechanical adjustments during the offseason, moved over on the pitching rubber to change the angle on his pitches, and opponents' at-bats told him throughout spring training that he was ready for a bounce-back season.

He talked of pitching 200 innings and being a rock in the Twins starting rotation. And he clearly has been more effective during the two starts he made this season than he was last year.

But his big plans are uncertain now, because he walked off the Target Field mound in the sixth inning Saturday and headed straight for an MRI exam on his right shoulder. The Texas Rangers' Nelson Cruz had reached on a single and Blackburn had a 2-1 count on David Murphy when manager Ron Gardenhire and trainer Dave Pruemer went to the mound to check on the pitcher. After a few minutes, Blackburn was walking off the field with Pruemer and the Twins' rotation woes were taking another turn for the worse. Blackburn was diagnosed with posterior shoulder stiffness and was listed as day-to-day.

The Twins lost 6-2 despite amassing 14 baserunners against Rangers righthander Yu Darvish. But they couldn't follow through all afternoon. Stranding 15 baserunners for the game -- including five at third base -- sends most teams home frustrated. The Twins had the additional issue of wondering what will become of Blackburn, who did not return to the clubhouse after the exam.

Twins General Manager Terry Ryan said Blackburn "cramped up" in the area while pitching but didn't want to speculate on the injury until he learned the results of the MRI.

The Twins' projected starting rotation will not get on the field this season. Righthander Scott Baker, expected to lead the rotation along with lefthander Francisco Liriano, battled elbow problems during spring training and will have surgery on his flexor pronator tendon on Tuesday, ending his season before it really began. Righthander Jason Marquis left spring training for two weeks to be with his daughter after she was seriously injured in a bicycle accident.

Righthander Anthony Swarzak was pressed into service for two starts, including Friday's, when Marquis' replacement, Liam Hendriks, suffered food poisoning last weekend. Marquis will start on Wednesday in New York, and there's a chance that Swarzak will have to start Thursday against the Yankees, depending on what happens with Blackburn.

The Twins don't have much starting pitching depth. With Baker out, they needed Blackburn to step into the void. Now, someone might have to step into the void left by Blackburn.

Twins starters entered Saturday with no wins and a 6.42 ERA. Blackburn was in the middle of a duel with Darvish, and the Rangers added two runs in the seventh and ninth after Blackburn left the game.

The hitting has shown signs of being reliable, the Twins batting .315 during the homestand. Denard Span went 3-for-5 on Saturday to lead a 13-hit attack, and Josh Willingham became the first Twin to open the season with an eight-game hitting streak since Shannon Stewart in 1994. The Twins hope that going 2-for-16 with runners in scoring position, as they did Saturday, will rarely happen.

"Left way too many out there," Gardenhire said.

A functional offense, however, will be wasted if the pitching doesn't stabilize. And the Twins need Blackburn's injury to be minor.

"Hopefully he's not hurt,'' Ryan said. "We don't need that."