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7/10/2013 12:07 A.M. ET

Johnson not worried about Harper in Derby

PHILADELPHIA -- Some managers get concerned that their players might mess with their swings by competing in the Home Run Derby.

Davey Johnson does not have that worry about Bryce Harper.

"It would [mess up someone's swing] in a lot of cases, but Bryce is swinging as hard as he can all the time anyway," Johnson said as he cracked a smile.

Harper was selected by the Mets' David Wright to be one of the National League's representative's in the Home Run Derby, which will take place on Monday on ESPN at 8 p.m. ET at Citi Field.

Harper, 20, is making his second All-Star appearance in as many seasons, and the outfielder entered Tuesday with 13 homers in 52 games this season.

"He's as strong as anybody there, so why not?" Johnson said.

Harper, last season's NL Rookie of the Year, joins Wright and the Rockies' Carlos Gonzalez and Michael Cuddyer as the Senior Circuit's participants in the event. Johnson said he did not know if Harper had picked who would throw to him during the competition.

Hairston debuts in left field for Nationals

PHILADELPHIA -- Scott Hairston has great numbers against Cole Hamels, and he was the first batter the lefty saw on Tuesday.

Hairston, whom the Nationals acquired from the Cubs on Monday, batted leadoff and played left field in his first game with his new team.

The journeyman outfielder, who popped out against Antonio Bastardo to end the game, went 2-for-5 in the Nationals' 4-2 loss to the Phillies.

Hairston, who entered play Tuesday 12-for-30 (.400) with five homers, five doubles, nine RBIs and a 1.521 OPS in his career against Hamels, wasted no time continuing that trend by singling in his first at-bat.

"I expect him to not get cheated up there," manager Davey Johnson said of the Nationals' newest player. "In his career against this guy, he's hit him great, and it's a good time to welcome him to the club."

Even with his numbers against Hamels and a .307 lifetime average against the Phillies, Hairston said he does not put much stock in previous performance. When one reporter asked him about his ridiculous numbers against Hamels, Hairston replied, "ridiculous, like bad?"

"Each day is different. He might pitch me different than he's ever pitched me tonight," Hairston said. "I don't know what's going to happen. I just try to put myself where I'm in a good hitter's count and I got to see what he's working with."

The veteran outfielder did not play in the Nats' series-opening loss Monday, and he said his flight was delayed twice coming to Philadelphia. But he was welcomed when he finally arrived at the field. Washington is the sixth stop in a 10-year Major League career for Hairston, and he noted it was nice to see the familiar faces of former teammates Gio Gonzalez, Kurt Suzuki and Chad Tracy in the Nationals' clubhouse.

Hairston was brought to the Nationals to primarily come off the bench and face left-handers, according to general manager Mike Rizzo. The 33-year-old said he is comfortable in that role, and is happy to be involved in a playoff push.

"I haven't been in a winning environment in quite a while," Hairston said. "It feels good."

Span sits vs. Hamels; Harper shifts to center

PHILADELPHIA -- The Nationals' starting outfield had a different look to it Tuesday.

Newly acquired Scott Hairston got the start in left field, Bryce Harper shifted to center and Denard Span was on the bench against Cole Hamels, a left-handed starter.

Span, a left-handed batter, is hitting just .154 with just two extra-base hits and one RBI in 91 at-bats against left-handed pitching this season. The Nationals acquired Hairston to have an outfielder who could come off the bench and face lefties. Hairston will also start Wednesday against southpaw Cliff Lee, and manager Davey Johnson is happy to have more outfielders at his disposal.

"I think he'll come out of it," Johnson said of Span's slump against lefties. "But I also think it sends a message to our league that I will use Hairston in his spot. And it also causes problems for other managers when they go to their bullpen, that I might hit Hairston."

The start in center field was the first for Harper this season. He's played one game there, but shifted to center after starting the game in left field. Harper did get a lot of center-field experience under his belt last season, and Johnson did not seem to think the switch would be a problem for the 20-year-old.

"I talked to him yesterday, I said 'Harp, you think your legs are good enough to play center field?' " Johnson said. "[He said] 'Yeah, oh yeah, oh yeah, I'm ready to play center.' He likes playing center field. He can run around and rumble."

Worth noting

• The Nationals are 41-10 when they score three or more runs this season, and 5-33 when they score fewer than three. They lost, 3-2, on Monday.

• Kurt Suzuki was behind the plate for the Nationals on Tuesday. He entered the night hitting .333 (8-for-24) in his last six games.

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