OAKLAND -- Like Neil Walker said, it could have been worse.

Still, when the second baseman hit his head against right fielder Ryan Church's knee Friday in an attempt to catch a foul ball along the right-field line, it looked bad.

Walker temporarily lost consciousness, walked off the field and stayed at a nearby hospital's intensive care unit for tests and observation. When he popped into the clubhouse a few hours before Saturday's game against the Oakland A's, teammates greeted him with, "How ya' doing, Walk?"

It was "basically a mild concussion," Walker said. Other than the headache and fatigue from lack of sleep in the hospital, he feels OK. He underwent a CT scan, blood tests and had his blood pressure checked every hour.

"I don't remember getting hit," Walker said, still wearing his hospital ID tag and joking that, "Fortunately, Church has soft knees."

Walker will be evaluated by doctors in Pittsburgh on Monday, manager John Russell said. He hasn't decided on roster adjustments to accommodate the injury just yet.

"We don't need to think about that right now," Russell said. "We'll know more after Monday."

Following the collision, Bobby Crosby moved from shortstop to second base, and Ronny Cedeno entered the game at shortstop. Crosby was slated to start at second Saturday, with Pedro Alvarez at shortstop.

Walker was a triple from the cycle at the time of the injury. He doubled in the first, singled in the third and hit a solo home run in the fifth.

McCutchen takes demoted Jackson's spot

OAKLAND -- The worst kept secret with the Pittsburgh Pirates is out.

Like was expected but wasn't officially announced until Saturday, reliever Steven Jackson was optioned to Triple-A to make room for Daniel McCutchen, the starter for Saturday's game against the A's.

Jackson suffered the loss Thursday in Texas after being recalled earlier in the day. At Triple-A, he went 1-0 with a 2.90 ERA in 22 relief appearances.

Saturday's start is McCutchen's fourth of the season. He's 0-2 with a 13.50 ERA in three starts and four appearances with the Pirates.

He was better in Indianapolis -- 4-5 and a 3.86 ERA in 10 starts -- and manager John Russell said he was emphasizing consistency with McCutchen.

"Down in the zone, use of all his pitches, command of his pitches," Russell said of the other keys. "His fastball is big. He had some shoulder fatigue and arm fatigue. He came back from that and started pitching much better, much more aggressive. He used his arsenal and also fastball command. ... I told him, 'You don't need to change just because you're here.' "

Worth noting

Saturday's game is the "1970s turn Back The Clock Game" at Oakland Coliseum, and the Pirates are in on it, too. While the A's are wearing their bright gold jerseys, the Bucs are wearing black pants, black tops and the gold bucket caps. Ryan Church and Delwyn Young must like the caps -- they were wearing them in the clubhouse hours before game time. ... Andrew McCutchen snapped an 0-for-12 streak with a single in the first inning Friday. ... Neil Walker's solo home run Friday snapped the team's six-game homerless streak.