SAN FRANCISCO -- The first-place Washington Nationals begin a nine-game road trip through California when they start a three-game set in San Francisco against the Giants on Monday.

Washington (30-19) will have its manager back as Dusty Baker returns after missing the weekend series against the San Diego Padres to attend the high school graduation of his son. The Nationals, under bench coach Chris Speier, went 2-1 in his absence.

San Francisco (22-30) won the final two games of its weekend series with Atlanta after dropping four games in a row. When somebody told San Francisco manager Bruce Bochy on Sunday, "You're on a mini-streak," he chuckled.

"Yeah, mini," he said. "But we want to keep making progress. We're facing the team leading their division. We've got to be on the top of our game. We'd been doing a good job, until the Cubs."

That was the beginning of last week in Chicago. After winning the opener of a series at Wrigley Field, the Giants lost three in a row to the Cubs, then fell in the series opener at home against Atlanta, scoring only six runs in the four games.

"It's been a struggle," Bochy said.

The Nationals, who are in a 12-game stretch in which they play every California team except the Los Angeles Angels, send Tanner Roark (4-2, 4.32 ERA) to the mound Monday after capping a 4-2 homestand with a 5-3 loss to San Diego on Sunday.

"We had some opportunities to score some runs, but we left some men on base early," Speier said.

Roark snapped a four-start winless streak (0-2, 6.35 ERA) when he allowed one run in seven innings of a 5-1 victory over the Seattle Mariners on Wednesday.

"It was good to get runs on the board early," Roark said. "So I relaxed a little bit out there and (made) my pitches."

Roark is 5-0 with a 2.51 ERA in six career games (three starts) against San Francisco, including 2-0, 3.52 in three appearances (two starts) at AT&T Park. He was 2-0 against the Giants last season, allowing one run in 14 innings over two starts.

San Francisco counters with left-hander Matt Moore (2-5, 5.28), who has recorded three consecutive quality starts. Moore is coming off a 5-4 loss to the Cubs in Chicago on Wednesday in which he yielded four runs (three earned) in six innings.

The Giants are 13-11 at home.

"We have to do something now that we're here," Bochy said of the six-game homestand. "It's our chance."

The Nationals rested regulars Bryce Harper, Daniel Murphy, Matt Wieters and Jayson Werth on Sunday with Murphy missing his third straight start. He was ill Friday and Saturday, but he appeared Sunday as a pinch hitter, as did Wieters and Werth.

Harper (.337 batting average, 15 home runs, 41 RBIs) is struggling of late, going 6-for-39 (.154) with two homers and five RBIs over his last 10 games. His average dropped 51 points during that span.

Monday's venue may not do Harper any good, as he is hitting .196 with two homers, six RBIs and 14 strikeouts in 51 at-bats at AT&T Park.

San Francisco hopes the sight of Roark gets Buster Posey going. Posey, who is 0-for-11 with five walks over his past four games, is 5-for-12 with three doubles and an RBI versus Roark.

Posey is batting .333 with seven home runs and 11 RBIs this season.