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3/1/2014 3:55 P.M. ET

Time for a 'change': Zimmermann adding to repertoire

VIERA, Fla. -- Jordan Zimmermann has enjoyed plenty of success in the Majors while riding his four-seam fastball, slider and curveball. At the same time, the development of a fourth pitch, the changeup, has been a frequent topic of discussion.

The Nationals right-hander used the offering effectively Saturday afternoon against the Braves at Space Coast Stadium, in his first Spring Training start. Zimmermann mixed it in while tossing two scoreless innings that included one infield hit, one strikeout and four ground-ball outs.

"Trying to carry the changeup over to March, and I guess it's March 1 today, so I'm taking a step in the right direction," said Zimmermann, an All-Star last year while going 19-9 with a 3.25 ERA. "Just keep throwing it and throwing it and throwing it is all you can do, because it's such a feel pitch that throwing it is the only way you're going to get better at throwing the pitch."

Zimmermann used the change 5.2 percent of the time last season, according to brooksbaseball.net, which was more than twice as much as in 2012.

He said he broke out the pitch a couple of times while facing the Braves' Freddie Freeman in the first inning.

"I threw one 1-0, and he kind of looked at me like, 'Really? We're starting this already?'" Zimmermann said. "But it was good. Got to 3-2, and I figured that was the last thing he was looking for and I threw a pretty good one. It was up a little bit, but he rolled it over and I got a ground ball, so it was good."

Robertson aiming to earn spot as lefty reliever

VIERA, Fla. -- Left-hander Tyler Robertson picked up his first save of the spring in the Nationals' 5-4 victory over the Mets on Friday. He was able to have a quick 1-2-3 inning in the ninth by using his breaking ball. It helped that he changed his mechanics during the offseason and reverted to the pitching style that helped him get drafted by the Twins in 2006.

"I did some stuff with my lead arm. It felt good," Robertson said. "I feel like it's more repeatable than what I've been doing. I want to incorporate that. For the first time against the hitters, I felt good. The ball was moving. Hopefully everything else falls into place."

Robertson spent seven-plus seasons in the Twins' organization before he was claimed off waivers by the Nationals last June. Robertson doesn't have any excuses as to why he struggled with Minnesota. He plays the game with a positive attitude and is hoping to make the team as a reliever. For now, the only lefty that is guaranteed to be in the bullpen this season is Jerry Blevins.

"The Nationals have something special going on over here." Robertson said. "That's my main focus. It if doesn't happen for whatever reason, I will go down to [Triple-A] Syracuse. If I go to Syracuse, I know I have to throw well right out of the gate. You never know what can happen at any time. My goal this spring is to be 100 percent ready."

Robertson is the son of Jay Robertson, the special assistant to Washington general manager Mike Rizzo. Tyler is pleased to be on the same team as his dad. In fact, he calls Jay his biggest supporter.

"He always helps me out," Tyler said about his dad. "It's awesome being on the same team that he is involved with. This is my ninth season playing [in professional baseball]. It's always been fun being in pro ball. He always has my back and he is there to keep me sharp. It's neat being on the same team as your dad."

Williams won't alter Walters' power stroke

VIERA, Fla. -- Former Nationals manager Davey Johnson encouraged shortstop prospect Zach Walters to be more of a power hitter, and Walters seemed to embrace that last season. He thumped 29 home runs and slugged .517 at Triple-A Syracuse.

The downside was that Walters struck out 134 times in 134 games, hitting .253 with a .286 on-base percentage. In light of that, would new manager Matt Williams like the 24-year-old switch-hitter to dial back his approach? Walters did hit at least .300 at Class A in both 2010 and '11.

"I think his stroke is his stroke. It's very difficult to change a tiger's stripes," Williams said. "He has power from both sides of the plate. I think the maturation process is such that as he goes within his career, he'll learn that home runs come and you can't force them. You can't stand up there and say, 'I'm a power guy, and this is what I do,' and get away from your game, whatever it is. So I'd like to see him eventually become a .300 hitter with power.

"What that means to me is situations where he can turn on a baseball or he's ahead in the count or he knows what's coming, or whatever it is, he can go ahead and let her fly. But there's also times where he's just going to have to drive a run in and he can ease a single up the middle. That'll make his average go up, his RBIs go up, and he'll maintain the same power."

Walters doubled from both sides of the plate while coming off the bench at shortstop Friday, and he got the start at third base Saturday, ripping a single and drawing a walk in two plate appearances.

Espinosa to see time at both middle infield spots

VIERA, Fla. -- A day after starting at second base in the Nationals' Grapefruit League opener against the Mets, Danny Espinosa was back in the lineup at shortstop against the Braves on Saturday.

That's indicative of manager Matt Williams' plan to get Espinosa work at both middle infield spots. After Espinosa's 2013 season was riddled by injury and ineffectiveness, the Nats have said he will compete for the second base job with Anthony Rendon, but also could fill a utility role.

"We'll try to break it up evenly," Williams said. "Again, he's going to play out there along with Anthony and along with other guys that we need to play as well. But I want him to break it up and he'll see a lot of time at short, too. It's important that he does that and feels comfortable in both spots."

The Nats know Espinosa can field both positions at a high level. In Saturday's first inning, he nearly threw out leadoff man Jordan Schafer from deep in the hole, then turned a 6-3 double play and finished the frame by making a diving stop up the middle and throwing to first.

The question is whether he can rebound offensively from his .158/.193/.272 line of a year ago. According to Williams, the key is not to shorten Espinosa's swing, even though he has struck out in 27.1 percent of his career plate appearances.

"He takes healthy cuts because that's what he does," Williams said. "But [hitting coach Rick Schu] is talking to him about being able to … not necessarily cutting your swing down, but taking a little more of what the give you."

As a switch-hitter, Espinosa has more room for improvement from the left side, where his .671 career OPS is 116 points lower than his mark from the right side. Espinosa went 0-for-2 left-handed Friday. On Saturday, he fouled out right-handed and hit two hard groundouts left-handed.

Worth noting

• Nationals left-hander Ross Detwiler will start against the Yankees on Monday. He will be followed by Tanner Roark and Chris Young. Stephen Strasburg will start against the Braves on Tuesday.

Jayson Werth will play his first game against the Marlins on Sunday.

• Major League Baseball Players Association executive director Tony Clark and special assistant Dave Winfield led a contingent that visited Viera, Fla., on Saturday to talk with the Nats in an annual Spring Training meeting. According to Nats player representative Drew Storen, the new MLB rules regarding instant replay and home-plate collisions were discussed, and the meeting also gave young players unfamiliar with the union a chance to learn more about what it does.

This is the first year as executive director for Clark, who took over the job after Michael Weiner passed away in November, following a battle with brain cancer. Clark, who played 15 years in the big leagues, has worked with the MLBPA since 2010 and had been deputy executive director since July.

"Tony worked under Michael and learned from Michael," Storen said. "Michael was a great person and great leader for us, and it was an unfortunate situation, but having Tony Clark step in, he knows the game from both sides. He's an incredible leader and he has a real presence when he talks to the room."

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. Andrew Simon is a reporter for MLB.com. Follow him on Twitter @AndrewSimonMLB. This story was not subject to the approval of Major League Baseball or its clubs.