WASHINGTON -- Nationals manager Dusty Baker said this weekend that his team can't look too much ahead to an upcoming west coast trip, which begins Thursday with a game in San Diego.

"We have not played the west (coast teams). You want to get some momentum before you go there," Baker said.

The Nationals, who have won six of the last seven, will certainly get a chance to do that when they begin a three-game series at home Monday with the Chicago Cubs in a showdown of first-place teams.

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Last year, manager Matt Williams took some heat when he did not set up his rotation to have Max Scherzer pitch in a series against the New York Mets.

Baker won't make that mistake this year, as Scherzer (7-4, 3.57) is slated to start Monday against the Cubs, who will send Kyle Hendricks (4-5, 2.90) to the mound.

"You want to get some steam, get a bit of cushion" before heading west, Baker said.

The Nationals (39-24) are a season-high 15 games over .500 and have more than a cushion. They also have some luck as Jack Arrieta is not slated to pitch in the series for the Cubs, nor is Jon Lester.

"We haven't played a lot of teams in the Central," said Washington shortstop Danny Espinosa, who scored the game-winning run Sunday as the Nationals scored two in the ninth to beat the Philadelphia Phillies 5-4.

When the teams met May 5-8 in the Windy City, the Cubs won all four games by a combined score of 22-16.

Scherzer got the loss May 6 by a score of 8-6 as he was hit hard, while John Lackey picked up the win in that game.

Will the Cubs refuse to pitch to Harper in this series, just like they did in Chicago when he drew a ton of walks?

"I don't know," Baker said Sunday. "I haven't really thought about it. I'm thinking about the Phillies now. And then tomorrow I probably still won't think about it. Because thanks to the Cubs, they're the ones that changed my lineup."

Harper struggled after that series but has started to hit better the past week. He was given a rest day on Sunday by Baker, though he did reach on a pinch-hit single in the ninth to aid a winning rally.

A sweep may be asking too much for the Nationals against the Cubs.

Washington got its first home sweep since late April with three wins over the Phillies this weekend.

Chicago is 43-18 -- the best mark in the majors -- after an easy 13-2 win on Sunday over the Atlanta Braves. The Cubs had made three errors on Saturday but the Nationals shouldn't count on Chicago beating themselves.

"It was uncharacteristic," Cubs manager Joe Maddon said of the errors in Atlanta.

Said Washington's Espinosa: "The Cubs are really good."

The Nationals and their fans are about to find out just how good the Cubs are.

Baker said Sunday his next goal is to get the Nationals to 20 games over .500. Maddon also has goals.

"I have goals -- that was 25 over today," Maddon said Sunday to mlb.com. "If I have any short-term goals, it's to increase increments of five, and that's what I focus on more than anything."