Shota Imanaga threw seven scoreless innings, Michael Busch and Kyle Tucker slugged back-to-back home runs in the first, and the Chicago Cubs blanked the visiting Boston Red Sox 6-0 on Saturday.

Imanaga (7-3) allowed just five hits, while striking out five and walking one, helping the Cubs take the weekend series and win their fourth straight game. Matt Shaw, Pete Crow-Armstrong and Ian Happ each added solo homers for Chicago, which now holds the majors’ best record (59-39).

Boston starter Brayan Bello (6-4) allowed three runs on six hits in the loss, striking out four and walking one. Masataka Yoshida and Abraham Toro each tallied a pair of hits for Boston, which dropped its second straight game after posting a 10-game winning streak to end the first half.

The Cubs struck quickly in the bottom of the first, as leadoff batter Busch sent the first pitch he saw over the wall for his 20th of the season. Tucker followed up with his 18th of the year to give Chicago an early 2-0 edge.

After Dansby Swanson walked and Nico Hoerner singled to begin the second, Vidal Brujan drove in the Cubs’ third run with a sacrifice fly to left.

Boston threatened to mount a two-out rally in the top of the seventh, as Yoshida singled to right and Toro reached on an infield single, while Yoshida advanced to third on Imanaga’s throwing error. From there it took just one pitch for the Chicago lefty to escape the jam, as Connor Wong was retired on a fly out to second.

Chris Murphy replaced Bello in the seventh, striking out Reese McGuire before allowing rookie Shaw’s third homer of the year with one out.

In relief of Imanaga, Brad Keller struck out the side in the top of the eighth.

Chicago tacked on against Murphy in the bottom of the eighth, as Crow-Armstrong and Happ clubbed consecutive solo home runs to push the Cubs’ lead to 6-0.