However, they probably don't want their closest challenger to gain any more ground in the standings.After losing the opener with the Braves in disappointing fashion, the Nationals try to even the series Saturday in Atlanta.Washington (89-55) suffered a 2-1 defeat Friday, as Atlanta's Andrelton Simmons scored the winning run on shortstop Ian Desmond's throwing error with one out in the ninth inning. Simmons came in from third base after Tyler Pastornicky hit a one-hop grounder to Desmond, whose throw home was wide."We just had a little error at the end," manager Davey Johnson said. "Otherwise, it looked good. I don't worry about those mistakes. Our defense has been outstanding. It's just tough to lose that way."As owners of baseball's best record, the Nationals haven't had to swallow many difficult losses like that. The defeat was just the fourth in 16 contests for Washington, which still owns a 7 1/2-game lead over Atlanta (82-63) with 18 to play.The Nationals had little luck offensively in the opener, striking out a season-high 17 times, with 13 coming against Kris Medlen. The Braves won for the 20th time in a row when Medlen is the starter and have enjoyed similar success behind Tommy Hanson (12-8, 4.35 ERA), winning 12 of his last 16 outings.Hanson allowed two runs and four hits in 5 2/3 innings in Sunday's 3-2, 10-inning win over New York. The right-hander has permitted two runs in each of his last two starts after recording a 5.74 ERA in his first three since coming off the disabled list with a lower back strain.Hanson had varying results in his first two starts of the season against the Nationals, yielding two runs over seven innings in a win June 3 but giving up eight runs in four innings while not receiving a decision July 20. He served up two homers in each of those starts, with Steve Lombardozzi, Michael Morse, Bryce Harper and Ryan Zimmerman all going deep.Harper hit his 19th homer Friday and is batting .414 (12 for 29) with three home runs against right-handers since Sept. 4.Atlanta's Martin Prado finished with three hits in the opener -- his third three-hit game in the last six -- and is batting .478 with six doubles in his past five against the Nationals. He is 2 for 6 lifetime against scheduled starter Edwin Jackson (9-10, 3.85), while Michael Bourn is 5 for 12 with a triple.Pitching on his 29th birthday, Jackson yielded six runs and nine hits in 4 2/3 innings in Sunday's 8-0 loss to Miami. The right-hander has an 8.71 ERA in his two starts this month after posting a 2.79 ERA in his previous eight outings.That stretch started with a stellar showing against the Braves on July 21, when he gave up a Brian McCann solo homer and four singles while striking out nine over seven innings. He didn't get any help from his offense, though, and his bullpen gave up three more runs as he was saddled with a 4-0 loss.McCann, who got the night off Friday against left-hander Ross Detwiler, is 3 for 8 lifetime against Jackson.