The Washington Nationals' Bryce Harper appears to have found his.Seeking a 10th consecutive winning decision, Kennedy looks to slow down Harper as the visiting Diamondbacks and NL East-leading Nationals conclude a three-game set Thursday night.After posting a 6-0 record over his final seven starts last season, Kennedy is 3-0 with a 3.38 ERA through five turns in the rotation in 2012.Though he's off to the best start of his career record-wise, opponents are batting .299 against Kennedy -- significantly higher than the .227 he limited them to last season.The right-hander had a difficult time hitting his spots during Saturday's 3-2 walk-off loss at Miami, yielding one run, seven hits and three walks over 6 1/3 innings. Kennedy had issued fewer than three free passes in each of his previous 12 starts."Definitely, the whole night was a battle trying to throw strikes," Kennedy told MLB.com. "It wasn't very fun pitching like that, feeling like you had runners on every single inning. My fastball was up, my offspeed was up. ... I feel like I've had 'C' stuff every time (out)."Kennedy has had his way in this series of late, going 2-0 while allowing a combined three runs over 21 innings spanning his last three starts. In his last meeting with the Nationals (15-9), Kennedy tossed seven frames of six-hit ball during a 2-0 road win Aug. 23.Kennedy, however, has yet to face Harper, who after going a combined 2 for 9 in his first three big-leagues games, came up huge in Wednesday's 5-4 walk-off victory.The No. 1 pick in the 2010 draft went 3 for 4 and scored a pair of runs -- the second coming on Ian Desmond's game-winning homer off Diamondbacks closer J.J. Putz with two outs in the ninth inning."He was born for these situations," manager Davey Johnson said of Harper, who led off the ninth with a double -- his second of the game.While the Nationals had scored a combined seven runs during a season-worst five-game losing streak, they're hoping Wednesday's victory will get them back on track."You guys are asking the wrong questions," Desmond said. "We're in first place. We're playing good baseball."Arizona (13-12), meanwhile, saw both its overall three-game winning streak and four-game run at Nationals Park come to an end."It won't be the last time it happens to us this year," manager Kirk Gibson said. "We're playing good baseball. We just have to shake this one off and come back (Thursday)."Winners of nine of 12 at home, the Nationals give the ball to Ross Detwiler (2-1, 1.64).After allowing only one earned run over his first three starts, Detwiler was tagged for three in six innings of Friday's 3-2 road loss to the Los Angeles Dodgers.The left-hander was excellent in his only matchup against the Diamondbacks last season, surrendering one run and six hits in 6 2/3 innings of a 4-1 victory Aug. 22, earning the win.Detwiler will need to be wary of Justin Upton, who went deep for the second time in three games Wednesday. The slugging right fielder has gone 7 for 19 against lefties this season.