ST. PETERSBURG, Fla. -- A few hours after Dustin Pedroia suffered what appears to be a concussion and left Saturday night's game in the second inning, the Red Sox completed a four-player trade with the Baltimore Orioles in which they will receive second baseman Jemile Weeks.

Coincidence? Total coincidence.

The Orioles have been looking for a third baseman since Manny Machado was lost to a season-ending knee injury two weeks ago, according to a major league source, and the Red Sox didn't have a well-defined role for Kelly Johnson, whom they acquired for shortstop Stephen Drew at the July 31 nonwaiver trade deadline.

And so, the Sox agreed to send Johnson and infielder Michael Almanzar to Baltimore for Weeks and infielder Ivan De Jesus Jr. Weeks is expected to join the Red Sox in Tampa, while De Jesus will be assigned to Triple-A Pawtucket, manager John Farrell said.

As it turns out, Weeks might play sooner and more often than the Red Sox expected. Pedroia was struck on the side of the head by a seemingly accidental elbow from the Rays' Logan Forsythe, who slid head-first into second base while advancing on a sacrifice fly by Ryan Hanigan in Tampa Bay's 8-0 victory at Tropicana Field. After reviewing the play, Farrell said he didn't believe Forsythe intentionally tried to hit Pedroia. Forsythe said that was "absolutely not" his intention, adding that he's "not that kind of player" and simply attempted a "swim-move" to avoid the tag.

Pedroia experienced dizziness on the field, according to Farrell, and was removed from the game immediately. Although his symptoms improved as the game went on, he was scheduled to see a doctor in Tampa and the Red Sox planned to monitor him overnight.

Brock Holt took over at second base and would be the first choice to play the position if Pedroia is sidelined for several games. But Weeks, 27, is a natural second baseman who has also played shortstop, left field and center field this season for the Orioles' Triple A club. After batting .303 with a .761 OPS and 22 stolen bases in 97 games as a rookie in 2011 with Oakland, he slipped to .221 with a .609 OPS in 2012 and has played only 11 games in the majors over the past two seasons.

Johnson, meanwhile, appeared in only 10 games for the Red Sox, going 4-for-25 (.160) with one RBI. He has now played for all five AL East teams, including the Yankees, Red Sox and Orioles this season.

"Yeah, it's crazy. Obviously I'll be familiar with the surroundings (in the AL East)," Johnson said. "It's exciting. It's cool to be in the playoffs or to be on a team that's in first and going to the playoffs. I'll be excited to get there and try to contribute and do some good things."

The Orioles were interested in reacquiring Almanzar, who was selected from the Red Sox in the Rule 5 draft last year but was returned in July when they didn't have a spot for him on the 25-man roster.

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Red Sox acquire Jemile Weeks from Orioles for Kelly Johnson