PITTSBURGH -- Right-hander Jeff Karstens, who went on the 15-day disabled list Wednesday with an inflamed right shoulder, was examined by team doctors on Thursday.

"We got the report and we're going to treat him and take care of him medically," Pirates' manager Clint Hurdle said. "There will be no throwing for seven to 10 days and then we'll go back to building him up.

"We'll take it one step at a time, he's got to get well enough to throw first and then we've got to get him back out on a rehab assignment, start off with a number of pitches that we are comfortable with and then build him back up to close to 80 to 100 pitches. I can't give you a timetable.

Right-hander Brad Lincoln is tentatively scheduled to make a spot start on Monday against Colorado, taking Karstens' spot in the rotation.

Burnett set for another rehab start Saturday

PITTSBURGH -- Right-hander A.J. Burnett is scheduled to make a fourth rehab start on Saturday with Double-A Altoona.

Burnett underwent surgery for a broken right orbital bone on March 2 and was placed on the 15-day disabled list retroactive to March 26. He threw a bullpen session on Wednesday at Chase Field in Phoenix.

"We'd like to see him go past 80 pitches and as close to 100 as he can, and be productive and efficient, that would be our goal," Pirates manager Clint Hurdle said.

Burnett made two rehab starts with Class A Bradenton and went 0-2 with a 12.79 ERA. He threw 81 pitches and gave up seven hits and five runs in four innings for Triple-A Indianapolis on Monday.

"The results really don't matter that much," Hurdle said. "You are dealing with a whole different animal down there with A-ball hitters and big league hitters. It sounds funny, but it's real. If you follow these things you see it, so what we're looking for is the crispness to the pitches, the location and is he following the glove, does he have arm slot command and is the ball sinking, what's his slider doing, what's his curveball doing and changeup."

Hanson lighting it up for Class A Power

PITTSBURGH -- Class A West Virginia Power shortstop Alen Hanson is off to a sizzling start offensively and leads the team with a .400 batting average through the first 14 games of the season.

After only hitting two home runs in 55 games in 2011, Hanson, ranked No. 16 on the Pirates' prospect watch list according to MLB.com, has already gone deep four times this season with 10 RBIs.

"I'm not surprised," Hanson said. "When I have a good swing and can feel that good swing, I know that I have some juice and wiry strength."

"Hanson has intriguing talent," said West Virginia Power hitting coach Edgar Varela. "We've seen his tools already. He's got some power. He can also do the little things. He can run, he can bunt, he plays a premier position, but most importantly, he's young.

"He's 19. And he hits from both sides of the plate."

Worth noting

• Entering Friday's series opener against the Cardinals, the Pirates had gone a season-high 29 consecutive innings without an error.

• The Bucs' bullpen ERA of 2.18 entering Friday ranked second in the National League behind San Diego (2.03). Only Los Angeles (5-2) and Washington (5-2) had more relief victories than the Pirates (4-2).