San Francisco (46-41) at Washington (39-49)

The Washington Nationals turned to their top pitching prospect to take their series opener against the San Francisco Giants on Friday night. The Giants will do the same in the finale as they try to head into the All-Star break on a high note.

Coming off his first major league win, San Francisco’s Madison Bumgarner(notes) takes the mound as the Giants and Nationals close the first half Sunday.

Washington (39-49) handed the ball to Stephen Strasburg(notes) for the opener of this series, and the rookie right-hander delivered a dominant performance in the 8-1 victory. Now, the Nationals will face the Giants’ most promising pitching prospect.

Called up in September to make his major league debut, Bumgarner (1-2, 2.86 ERA) spent the first three months of the 2010 season with Triple-A Fresno before rejoining the Giants (46-41) in late June. He posted a 4.50 ERA while losing his first two starts, but looked more like the 10th overall pick of the 2007 draft in a 6-1 win at Milwaukee on Tuesday.

The 20-year-old left-hander scattered three hits while striking out five over eight scoreless innings.

“It’s a very humbling experience to get a win up here,” he said. “This is the best there is. I’m just glad to be pitching up here.”

Giants catcher Buster Posey(notes) doesn’t doubt Bumgarner belongs in the majors in spite of his age.

“To me, it’s his third quality start in a row,” Posey said. “He threw the ball in and out really well, had that cutter working, was able to throw the changeup for a strike when he needed it, and then later in the game he started flipping curveballs in. He did a great job.”

Bumgarner will have a good chance at another victory if San Francisco can continue its offensive surge. Even though they were shut down by Strasburg, the Giants have averaged 7.6 runs while winning six of eight, including a 10-5 victory over the Nationals on Saturday night.

Posey hit a tiebreaking single in a four-run seventh inning and added a two-run homer that withstood a video review. It was his seventh homer since being recalled from Fresno on May 29 and his sixth in 10 days. The 23-year-old is hitting .514 with 13 RBIs in July.

“I try not to have too many expectations,” Posey said. “I try to set myself a goal, whether it’s for a year or a week or a day - just go out and play as hard as I can and the results take care of themselves.”

Posey hopes to continue his surge against Livan Hernandez(notes) (6-4, 3.12), who will take the mound for the Nationals looking to snap a three-start winless streak. The veteran right-hander won four of his first five starts of the season, but is 2-3 in his last 12 after failing to get a decision in Washington’s 6-5 win over San Diego on Tuesday.

Hernandez, who gave up four runs and nine hits in seven innings in that game, is 1-2 with a 7.81 ERA over his last five starts against San Francisco, including a 4-2 road loss May 25.

San Francisco’s Aubrey Huff(notes), batting .343 with five homers and 12 RBIs in July, is 6 for 13 with two homers against Hernandez. Aaron Rowand(notes) is 9 for 20 with two homers and two doubles against him, while Pablo Sandoval(notes) is 6 for 17 with a homer and three doubles.