WASHINGTON - Dexter Fowler had two hits, scored twice and Jason Hammel continued his mastery of Washington Nationals in the Chicago Cubs' 4-2 win on Saturday.

Hammel (5-2) improved to 9-0 with a 3.01 ERA in 11 starts against the Nationals. Anthony Rizzo and Jonathan Herrera each had two hits and drove in a run for Chicago.

Hammel allowed a run on five hits in eight-plus innings, striking out seven and walking two. He departed after Bryce Harper hit his 19th homer of the season to open the ninth.

After Hector Rondon walked Anthony Rendon, Pedro Strop came on and recorded his second save.

Wilson Ramos also homered for the Nationals.

With starting pitchers Stephen Strasburg and Doug Fister on the disabled list, the Nationals called on 22-year-old prospect Joe Ross (0-1) to make his Major League debut. Ross, who was 2-2 with a 2.81 ERA at Double-A Harrisburg, retired the first nine Cubs, but allowed a run in the fourth and two in the fifth.