Ian Kennedy is off to another good start for the Arizona Diamondbacks and will try to stay unbeaten when he takes the mound tonight against the Washington Nationals in the finale of a three-game series.

Kennedy opened the 2011 campaign 6-1 and finished 21-4 with a superb 2.88 earned run average in 33 starts. It's been so far, so good for Kennedy this season as evidenced by his 3-0 record and 3.38 ERA in five outings. He did not figure into the decision of a 3-2 loss at Miami his last time out on Saturday and was reached for just one run and seven hits in 6 1/3 innings.

The All-Star right-hander struck out five Marlins batters and has fanned at least that many in four straight starts. Kennedy will make his fifth career start against Washington and is 2-1 with a 2.52 ERA in the first four.

Arizona could use a lift tonight after blowing a two-run lead in the bottom of the night in Wednesday's 5-4 loss at Nationals Park. Ian Desmond cranked a game-winning two-run home run off of Diamondbacks closer J.J. Putz, sending Arizona to its second loss in six games.

"He got hit pretty hard. The fastball wasn't exactly where we wanted it. It happens," Arizona catcher Miguel Montero said.

Joe Saunders entered the game with baseball's best ERA at 0.90, but allowed three runs -- two earned -- and seven hits over 6 1/3 innings.

Justin Upton homered for the second time in three games, Ryan Roberts drove in two runs and Montero ended with three hits for the D'Backs, who are 4-2 on a 10-game road trip and will visit the Mets for three games this weekend.

Desmond's home run ended Washington's season high five-game slide and made a winner out of reliever Henry Rodriguez. Rodriguez tossed a scoreless top of the ninth and starter Edwin Jackson was bailed out after he permitted four runs and eight hits through the first six innings.

Bryce Harper had three hits, an RBI and scored twice in the win.

"It was unbelievable, great win for the club and just a really exciting time for us and exciting to be a part of that," Harper said.

The Nationals lead the NL East by one-half game ahead of Atlanta and will welcome Philadelphia to the nation's capital for three games this weekend. The Phillies sit 3 1/2 games off the division lead.

Ross Detwiler is coming off his first loss of the season and will take the ball for the Nationals tonight. Detwiler gave up three runs and five hits over six innings of a 3-2 setback at Los Angeles last Friday, falling to 2-1 in four starts to go along with a strong 1.64 ERA.

Detwiler entered the matchup with the Dodgers sporting a microscopic 0.56 earned run average. The lefty is 1-1 with a 4.22 ERA in two career starts against the Diamondbacks.

The Diamondbacks and Nationals are meeting for the first time this season, and Arizona won five of the eight encounters a year ago. The D'Backs were unbeaten in the previous four matchups until last night's late-inning loss.