OAKLAND --- The seventh inning was frustrating enough for the Pittsburgh Pirates, but a collision between two players made it even worse.

The Pirates began the frame trailing just 5-4, but the A's scored seven runs en route to a 14-4 win. Perhaps more damaging, though, was Neil Walker's injury, which he suffered in the inning.

With no outs, Oakland's Kevin Kouzmanoff popped the ball up along the right-field line. Right fielder Ryan Church and Walker both charged for it. Walker appeared to hit his head against Church's knee as the ball fell between them.

Walker remained on the ground as the team's medical staff examined him. Minutes later, he left the field on his own power, exiting the game.

Walker was taken to the Alta Bates Summit Medical Center in Oakland for evaluation, but he was coherent and undergoing tests. The club did not disclose the nature of the injury, only that Walker hit his head.

Manager John Russell said that he didn't think Walker lost consciousness. Walker did not move much when he went down.

"He was close," to being unconscious, Russell said. "The initial shock got him. He didn't feel nauseous or anything. We're hoping for the best."

Pittsburgh starter Brad Lincoln, who had just exited the game, said that Walker appeared in the clubhouse after his collision and looked OK.

"He's a tough guy," Lincoln said. "He plays hard and sometimes that happens when you do that."

Following the collision, Bobby Crosby moved from shortstop to second base, and Ronny Cedeno entered the game at shortstop.

Walker was a triple away 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.

Crosby returns to roots in Oakland

OAKLAND -- After nine years with the Oakland A's organization, one would think Pirates infielder Bobby Crosby had seen all of the Oakland Coliseum.

Turns out, he had never been to the visitor's clubhouse. He saw it for the first time on Friday before his current team began a three-game series here. It was the first return to Oakland for Crosby, whom the Pirates signed as a free agent during the offseason. Crosby went 0-for-4 with a strikeout at the plate, spending time at shortstop and second base.

Like the sign says in front of the room, he was, indeed, a visitor, especially foreign in this case.

"It's really strange," Crosby said. "I had never been to this side before. It was weird coming to the park, knowing that I'd be on this side."

Crosby was Oakland's first-round pick in 2001 and spent parts of seven seasons in the Major Leagues with A's, years that began with promise until injuries slowed him down. He was the American League's Rookie of the Year in 2004, a highlight among many in his tenure with Oakland, the shortstop said.

"The first couple of years were great," said Crosby. "Then I had some injuries; I had some struggles. Things went a little differently than I had hoped. I still have a lot of good memories. I made a lot of good friends."

Crosby said that he never forgot the coaches, teammates, clubhouse attendants and video assistants.

Milledge's absence unrelated to confrontation

OAKLAND -- Outfielder Lastings Milledge was not in the Pirates' starting lineup Friday against A's right-hander Ben Sheets.

According to manager John Russell, it is unrelated to the heated exchange that Milledge had with bench coach Gary Varsho in the sixth inning of Thursday's loss at Texas, when Milledge was thrown out at second base.

Russell said Friday that Milledge's absence from the series opener against the A's has only to do with matchups. Ryan Church was penciled in to start in right field on Friday, where Milledge was Thursday. Delwyn Young, a switch-hitter who did not play Thursday, was set as the designated hitter, where he's hit in two previous Interleague games this season.

"[I] wanted to get DY in there," Russell said. "[Young] had some decent at-bats the other night. ... I wanted to use the DH slot to get another left-handed bat in there, which we've done. I guess people might say [it was] because of last night, but we've done that with Lastings.

"We'll continue to make some adjustments as we go, looking at matchups and how it works out. But no, it had absolutely nothing to do with last night."

During a hit-and-run, Bobby Crosby did not take swing. Crosby said on Friday that he missed the sign, and he downplayed talk that he, too, was involved in the conrontation.

"We put an end to it pretty quickly," Crosby said. "I'm not gonna let a little thing disrupt the type of atmosphere that we've got, guys that want to pull for each other."

Worth noting

Pirates shortstop Bobby Crosby, who until this season spent his entire career with the A's, said he will have his parents, among other family members, in attendance. ... Manager John Russell elected to tremove one of the team's hottest hitters from the starting lineup Friday. Lasting Milledge, named "Mr. Clutch" in the team's pregame media notes, has gone 10-for-22 in his previous seven games and 14-for-32 in his past 11. He's third in the National League with a .392 batting average with runners in scoring position. ... Crosby has four hits in his previous five at-bats with runners in scoring position, and Garrett Jones has seven hits in his last 10 such at-bats.