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2/22/2014 8:02 P.M. ET

Fister impresses new teammates in BP

VIERA, Fla. -- Nationals pitchers participated in live batting practice Saturday. Right-handers Chris Young and Taylor Jordan had their outings cut short because of the rain and will throw another time.

Of all the pitchers who threw on this day, right-hander Doug Fister stood out. He faced shortstop Ian Desmond, second baseman Anthony Rendon and catcher Sandy Leon. Fister looked like he was in midseason form. He declined to pitch with the pitching screen in front of him, because it's too much of a distraction.

"He pounded the zone," manager Matt Williams said. "We didn't let the guys at the plate know what was coming, [because we wanted to protect] Doug. He didn't have a screen in front of him. He threw everything for strikes. He worked pretty fast. He got a lot of pitches in today. He said he likes to feel tired and work through the tiredness. It was a good session for him today."

Desmond said Fister's changeup and sinker were impressive.

"He was competing. He was a little fired up. I like that," Desmond said. "I swung at a sinker, I swung over the top of it and it disappeared. He threw me a changeup and it looked exactly the same as the sinker. I can't tell the difference."

Rendon hit a home run off Fister during the session, but was still impressed by what he saw from the right-hander.

"He is tall and lanky, but he is fluid. He is so smooth on the mound. His ball just moves all over the place," Rendon said. "I wouldn't say I did well. It's just the first day."

Lefty pitching prospect Purke gets tips from Livo

VIERA, Fla. -- Nationals coach and ambassador Livan Hernandez watched left-hander Matt Purke throw his first live bullpen session on Saturday.

After Purke was done, Hernandez told the left-hander that he was getting lazy with his front side when he was throwing his breaking ball.

"He wanted me to stay strong on the offspeed and [follow] through," Purke said. "That way, those pitches would be up and over the plate. He said if you don't keep it strong, it's going to go down every time. Nobody will swing at it."

Purke, who was rated by MLB.com as the 6th best prospect in the Nationals' farm system in 2013, is finally healthy entering Spring Training. He had his throwing shoulder cleaned up before last season, and now he is ready to show the Nationals what he can do.

"I want to have a good spring and just go from there," Purke said. I can't control where they send me or what they do with me, but I can control what I do between the lines. My focus is to prepare and be the best I can be out there."

Williams meets with MLB to discuss instant replay

VIERA, Fla. -- Nationals manager Matt Williams, general manager Mike Rizzo and members of the staff traveled to Kissimmee, Fla., on Friday to gain a better understanding of the new instant-replay rules.

Teams including the Tigers, Astros and Braves were also at the meeting with MLB executive vice president Joe Torre and special consultant Tony La Russa. The meeting lasted 2 1/2 hours. Williams said he was pleased by what was said, but will not have a full grasp on extended instant replay until the changes are in place in the next week or so.

The new rules go into effect when the spring season starts. If a manager has a problem with a call, he is encouraged to go to the crew chief.

"Depending on the situation, timing is going to be important -- when you can or can't challenge, what that timing is," Williams said. "We learned what plays are challengeable, what aren't. They are still defining that as we speak. But they gave us an indication what would be, what wouldn't be and how to go about doing it, because nobody has ever done it."

Worth noting

• Williams has been impressed by shortstop Desmond. Williams said Desmond relishes his role as one of the leaders on the team.

"From what I've seen so far, he was the first one out for early work today," Williams said. "He is the first one to ask questions. He wants to know what we are thinking and how we go about our business. That's what you want from your middle infielder, your catcher, certainly, and your center fielder. Those guys are going to take charge on an everyday basis."

• After he was done catching live bullpen sessions at the Nationals' Minor League complex, a little boy went up to Jose Lobaton and asked if he could have his batting gloves. Lobaton did one better. He gave the kid a bat with his signature on it. The kid was ecstatic, of course.

Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.