Denard Span after collision with Dan Uggla on Friday. (AP Photo/David Goldman)

The Nationals made a flurry of roster moves on Saturday, including placing center fielder Denard Span on the seven-day disabled list for a concussion after a collision with second baseman Dan Uggla in the eighth inning of Friday’s wacky game. To take his place, the Nationals called up outfielder Steven Souza Jr. from Class AAA Syracuse. The Nationals also optioned rookie right-handed reliever Aaron Barrett and called up right-handed starter/reliever Blake Treinen from Syracuse.

Span is the most concerning development. The 30-year-old leadoff hitter suffered a concussion in June 2011 after a collision on the bases when with the Minnesota Twins. Span played only 70 games that season after the side effects of the concussion lingered for months. Another serious blow to the head prompts caution.

Span was rounding first base in the eighth inning on Friday after he smacked a game-tying single up the middle. Uggla was running toward first base when he collided with Span, who was knocked to the ground and his helmet was knocked off. After Manager Matt Williams and assistant trainer Steve Gober came out to check on Span, he remained in the game and finished the 10-inning contest. Span was awarded second base because Uggla obstructed his path on the bases.

Soon after the game, Williams said Span was fine. But at some point after the game, Span complained of a mild headache and was evaluated by a doctor, Williams said on Saturday. The doctor recommended that Span be evaluated on Saturday and, after a check-up, ruled that Span hadn’t passed the concussion test and was suffering from mild concussion symptoms, Williams said.

“He seems to be all right,” Williams said. “He’s had some history of it. He had a pretty serious one before. So we just want to make sure with that.”

Span remained at the team hotel Saturday. Williams was unsure if Span would travel with the team to Miami following Sunday’s game. Span would have to undergo a battery of tests after physical activity to rejoin the team. There are league protocols for when a concussed player can return to play. The seven-day disabled list was created in 2011 for players suffering from concussions or its symptoms.

Williams said Span was evaluated on the field by Gober after the collision. In between innings, Span was evaluated in the tunnel of the dugout by trainer Lee Kuntz, Williams said. “He said he felt fine then but after the game he said I’ve got a little bit of a headache, so that’s when the doctor evaluated him,” Williams said.

Souza, 24, who had an impressive spring training, was called up because he was playing well at Syracuse and because he can play all three outfield positions. The speedy and strong outfielder began the minor league season at Syracuse and was hitting .273/.429/.545 with two home runs in seven games. Souza arrived late but just before batting practice on Saturday and was listed on the lineup card so he is available. This is his first major league call-up.

The Nationals are using Bryce Harper in center field, Nate McLouth in right and Kevin Frandsen, who is traditionally an infielder, in left Saturday. That’s because McLouth is “a little more right-field friendly than Harp,” Williams said.