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8/15/2013 1:36 A.M. ET

Walden expected back for Nationals series

ATLANTA -- The Braves expect one of their most trusted eighth-inning weapons back by the start of this weekend's series against the Nationals. Right-hander Jordan Walden played catch on Tuesday for the first time since taking a line drive off the base of his thumb during Saturday night's 1-0 loss to the Marlins, and two more days without any setbacks should put him back in the bullpen by Friday night.

"I played catch yesterday but I could still feel it in my thumb," Walden said on Wednesday. "It's just a bruise, but it's still sore."

In Walden's absence, right-hander David Carpenter worked a scoreless eighth inning on Tuesday night to preserve a two-run lead in the Braves' 3-1 win after Kris Medlen walked the leadoff hitter.

"We'll see where he's at today, but he's progressing real well," manager Fredi Gonzalez said. "I wouldn't be surprised if he's available the whole weekend."

Newly called up Pastornicky exits with injury

ATLANTA -- Second baseman Tyler Pastornicky, called up on Tuesday when Dan Uggla went on the disabled list, left Wednesday night's game with a sprained left knee after colliding with right fielder Jason Heyward under a pop fly.

After an MRI is performed on Thursday, the Braves will determine Pastornicky's status for this weekend's series against the Nationals.

With one out in the top of the third inning, Phillies shortstop Jimmy Rollins sent a fly ball to shallow right field. Both Pastornicky and Heyward called for the ball, and Pastornicky appeared to be nearly camped under it before Heyward clipped his left side coming in hard from behind, hitting the back of Pastornicky's left calf with his knee. The ball dropped to the ground, and Rollins took second base on the miscommunication.

"As soon as that ball left the bat, Jason was calling for it and calling it loud," manager Fredi Gonzalez said. "We were on the field level, and you could hear it clearly that Jason was calling for that ball. I don't know if Tyler didn't hear him or was so locked in on that ball that he didn't hear Jason coming."

"I heard nothing," Pastornicky said. "That's one of those converging plays, and I just tried to yell as loud as I could, but I think he was just running in, and we just kind of met at the same time."

Heyward was told that other players had heard him call for the ball, and first baseman Freddie Freeman peeled away from the play early after being called off by one or both players.

"I called it early," Heyward said. "I was saying, 'Hey, I got it, you guys take it easy, you don't have to stretch for it,' but he kept going."

Pastornicky remained on the ground as Gonzalez and team trainers checked on him, and he returned to second base for the final two outs of the inning.

"It locked up pretty good to where I couldn't really move on it," Pastornicky said. "I tried to tough it out, I finished out the inning, but coming off the field, it just started locking up. It was pretty much time to come out then."

The injury cut short what appeared to be an extended opportunity for playing time for the 23-year-old utility player, who was one game into his third stint in the Majors this season.

Pastornicky was preparing to make his first start in left field for Triple-A Gwinnett on Tuesday afternoon when he was recalled by the Braves and told to head downtown for his first Major League start at second base since April 28. With Uggla out to undergo LASIK eye surgery, Pastornicky figured to be entrusted with holding down the right side of the infield until Uggla feels comfortable enough at the plate to return.

"I've taken a real liking to second," Pastornicky said prior to Wednesday's game. "I feel like it's probably my best position. I just feel a lot more comfortable there. Everything that I've gone through so far, the turns, have been smooth. It's been a pretty good transition."

Pastornicky made an early impact in each of his first two starts, shooting a single into right field in his first at-bat and scoring the first run of the game in the second inning of Tuesday's 3-1 win over the Phillies. On Wednesday night he legged out an infield single on a bouncing ground ball to the right side to extend the first inning.

Paul Janish earned his first start of the year at shortstop after the Braves opted to give Andrelton Simmons an extra day of rest ahead of this weekend's series against the Nationals. But that off-day was short-lived, as Simmons took over at shortstop to start the fourth and Janish moved to second in Pastornicky's place.

"He was scuffling, and we didn't want to take a chance," Gonzalez said. "We would have loved for him to finish the game healthy and give Simmons a day off and win the game. That didn't happen. Simmons went in and got a double and played defense. He got three innings off."

Pastornicky received positive feedback from the initial tests performed by team trainers and told reporters that he felt more pain from the bruise where Heyward came into contact with his calf than from the injured knee.

"I'm sure he's [feeling] pretty fortunate right now, because that's a bad matchup for him," Gonzalez said. "Six-foot-five compared to five-foot-10."

Worth noting

• Veteran outfielder Reed Johnson has taken batting practice and thrown in the outfield over the course of the current homestand, but his return from Achilles tendinitis is still several days off. Johnson has increased his walking elevation on the treadmill but he has not started running.

"I'm not waiting until it's 100 percent, I know that," Johnson said on Wednesday. "Those days are over, so I'm just kind of getting to a point where I can at least function as far as running and running down fly balls in the outfield, and once I get there, I'm going to ask to go out and play a few games and hopefully be back."

Eric Single is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.