Red Sox shortstop Julio Lugo was out of the lineup last night, suffering dizziness.

AP / Duane Burleson

MINNEAPOLIS — Struggling shortstop Julio Lugo was yanked from the Boston Red Sox’ starting lineup for last night’s game against the Minnesota Twins at the Metrodome.

Not for the reason that some might think.

It had nothing to do with the fact that Lugo already has committed a whopping major-league-leading total of 11 errors, the latest of which cost the Red Sox two unearned runs in a 7-6 loss to the Twins on Friday night.

No, Lugo was scratched because the Sox think he might have suffered a mild concussion in a baserunning collision with Minnesota second baseman Matt Tolbert on a fielder’s choice in the sixth inning of Friday night’s game.

Lugo was dizzy but stayed in the game. He also was dizzy, however, when he woke up yesterday morning, which was no surprise to trainer Paul Lessard, who told manager Terry Francona after it happened during the game that there may be some day-after issues.

So yesterday afternoon the Sox sent Lugo for tests.

Lugo was sliding into second on what should have been a routine forceout Friday night. But the throw from third baseman Mike Lamb to second base was high and wide. Tolbert had to go up to get the ball. He caught it for the forceout, but in the process, his knee banged the right side of Lugo’s head.

Lugo stayed down for a while as Francona and Lessard went out to check on him. But after only a short time Lugo was back on his feet.

“I was laying there because I was dizzy, and I was a little dizzy when I got up,” said Lugo. “I got hit pretty good. When I came to the bench, I was dizzy.”

There were a few moments when Lugo wasn’t sure if he could stay in the game, but his head cleared enough for him to do so.

Yesterday morning, though, he wasn’t clear-headed.

“I was feeling dizzy when I woke up,” said Lugo. “I have a headache. We’ll do some tests, but I’ll be all right. I’m OK.”

Physically he may be OK, but defensively he certainly has not been OK. He has more than half the team’s errors (Lugo 11, Red Sox 10) and they have been ugly ones. Take the error Friday night for example. It was a routine two-out bouncer right at him. The ball bounced up perfectly. He had his head down on the ball. But the ball clanged off his glove after hitting the pocket. The error ultimately cost starter Jon Lester two unearned runs in Boston’s 7-6 loss. The error came in the second inning, before Lugo got his bell rung, so that couldn’t be used as an excuse.

It was Lugo’s fourth error in the last eight games and his fifth in the last 13 games. Every ball hit to him seems to be a 50-50 proposition, such as Michael Cuddyer’s grounder in the eighth on Friday night. He fielded it cleanly but his throw was way wide of first on the home-plate side. Kevin Youkilis caught the ball and tagged out Cuddyer.

Still, Francona said he hasn’t necessarily seen signs that Lugo is in need of a day off for his own mental health, not to mention the Sox’ defensive health.

“I have seen him for the most part be more aggressive in the field, making plays in the hole, moving his feet, and then he makes an error,” said Francona before yesterday’s game.

The Sox, though, need better, more consistent play out of their shortstop than what Lugo is providing.

skrasner@projo.com