Updated

Washington, DC (SportsNetwork.com) - Tanner Roark tossed an effective 5 1/3 innings to help the Washington Nationals split a four-game series against the Atlanta Braves with a 4-1 decision in the finale at Nationals Park on Sunday.

Roark (7-4), who has allowed three runs or fewer in nine straight starts, yielded just one run on four hits and three walks to win a career-high fourth straight start.

Denard Span, Adam LaRoche and Ryan Zimmerman each drove in a run for the Nationals, who have won four of their last six and increased their lead to 1 1/2 games over the Braves for first place in the National League East.

"You have to play a clean game to beat a team of this caliber," said Span. "For us to close this series out with two wins is huge for us."

Ervin Santana (5-5) spun six innings, surrendering three runs on six hits while striking out nine. After starting the season 4-0, the righty is 1-5 in his last eight starts.

Evan Gattis, who went 0-for-3 with a walk, snapped his 20-game hit streak and Justin Upton had the lone RBI for the Braves, who have lost five of their last seven contests.

The Nationals scored two in the first to take an early lead. Anthony Rendon drew a walk and Jayson Werth followed with a base hit. LaRoche's single up the middle and Zimmerman's sacrifice fly put the runs on the board.

In the fifth, Sandy Leon led off with a base hit and moved to second on a Roark sac bunt. Span slapped an RBI double off the end of his bat to left, increasing the advantage to 3-0.

Freddie Freeman singled and Gattis drew a walk to start the sixth. Upton dropped a one-out single in right to plate Atlanta's first run and chase Roark from the game.

Chris Johnson thought he checked his swing on a slider from reliever Craig Stammen but he was called out then ejected for arguing the call. Andrelton Simmons grounded out to end the sixth.

"We did a good job of getting good counts but we just missed a couple opportunities," said Braves outfielder Jason Heyward.

Washington added an insurance run in the eighth. Rendon doubled and advanced to third on a groundout. He then scampered home on a wild pitch by Luis Avilan.

Rafael Soriano struck out the side in the ninth to collect his 17th save of the season.

Game Notes

Upton was ejected in the ninth for arguing after striking out by home plate umpire Mark Carlson... It was the first time the Nationals won two straight over the Braves this season ... The Braves had just nine hits and one run in the final two games of this series ... Washington is now 33-3 when scoring 4 runs or more ... Atlanta leads the majors with 53 quality starts.