Extra bases

• Olt will play first base again on Saturday, but soon he'll switch to the other side of the infield.

Olt has been limited to first base and designated-hitter duties to avoid aggravating his right shoulder, which has been tender. It's not bothering his hitting. On Wednesday, he belted two home runs and hit an RBI single against the Mariners.

"He got brushed back pretty good, up and in, and then they threw him down and in, mid-belt, and then he ended up stroking another knock," Renteria said of Olt, who apparently is seeing the ball just fine and is over the vision problems he had in the past.

"All things being equal, I think he's coming along and showing everybody he's back on track and who he was in the past," Renteria said of Olt, who was a highly touted prospect with the Rangers, and whom the Cubs acquired last July in the Matt Garza deal.

Jake Arrieta threw a side session on Wednesday, his third of the spring, and he hoped to face hitters in a live batting-practice session his next time. Arrieta has been slowed because of tightness in his right shoulder. He's been frustrated at being sidelined.

"The competitor in me wants to go [full tilt], but the more thought-out side of me knows this is the right thing to do to be a little slower and make sure everything is where it needs to be," Arrieta said. "You want to be functioning for a long season."

Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.