Erik Arnesen found a winning formula this spring – pound the zone with hard fastballs and keep hitters off balance with a deceiving splitter.

The big right-hander used that model – the one that brought him here in the first place – to perfection, striking out all three batters he faced in Wednesday’s Class AA Eastern League All-Star Game in Manchester, N.H.

Fellow Washington Nationals prospect Bill Rhinehart scored the go-ahead run. He smacked a fastball to the deepest part of the park in center for a leadoff double in the seventh inning. Two batters later, Charlie Culberson drove in Rhinehart to give the Western All-Stars a 3-2 lead in the West’s 8-3 win.

“I knew I hit the ball hard,” Rhinehart said, “but I didn’t know if it would have enough to get out. Since there were no outs, I just ran as fast as I could.”

Rhinehart and Arnesen were the top performers from the Nationals’ affiliate in Harrisburg, Pa., which sent six farmhands to the all-star game. The Senators lead the Eastern League’s Western Division by 5 1/2 games.

Rhinehart thanked chemistry for that.

“We have such a great team, mainly because of the chemistry we’ve built,” Rhinehart said, adding that he doesn’t expect the recent addition of Bryce Harper to change that. “Bryce is a good guy. We’ve got such a stable team that Bryce is just adding more talent, which will only help us.”

Arnesen, who is 6-1 with a 2.27 ERA, hit 97 mph on the stadium radar gun and needed just 14 pitches to strike out the side in the second inning.

A 17th-round draft pick of the Nationals in 2006, the 6-foot-3, 260-pound pitcher has mowed through Class AA since improving his splitter, which he added to his repertoire three years ago. He now sports a hard fastball, slider, curveball and the splitter, which he uses as his out pitch.

Arnesen has struck out 59 batters in 67 1/3 innings and limited the opposition to a .237 average.

“Things have started to come together for me,” Arnesen said. “My splitter has made the biggest difference.”

Hassan Pena, drafted in the 13th round in 2006 by the Nationals, took the mound in the seventh inning, recording a hold as he struck out two batters and allowed just one hit.

Tyler Moore, the Nationals’ minor league player of the year last season, went 0 for 5 with two strikeouts, while outfielder Archie Gilbert went 1 for 2. Both of them took part in the home run derby that occurred before the all-star game. Brad Peacock, Harrisburg’s ace, did not play after appearing in the Futures Game in Phoenix on Sunday. He is 10-2 with a 2.01 ERA and has struck out 129 batters in 98 2/3 innings.

Rhinehart’s double propelled the West to a two-run seventh before Pena came on in the home half of the inning.

“You just have to treat it like it’s any other game,” Pena said. “It can be tough because of the hitters and the atmosphere, but that’s what you have to do and that’s what I tried to do.”

The West added four runs in the ninth before allowing the game’s final run.