The Chicago Cubs walked Washington star Bryce Harper a record-tying six times, then beat the Nationals 4-3 when Javier Baez homered in the 13th inning Sunday for a four-game sweep.

The Cubs won their seventh in a row and improved the best record in the majors to 24-6. Washington, which had been leading the NL East, lost its fourth straight.

Manager Joe Maddon and the Cubs simply showed no interest in pitching to Harper. The regining NL MVP walked 13 times in this series.

Harper matched the major league record for walks in a game, last done by Jeff Bagwell in 1999. Harper was hit by a pitch the other time he came to the plate.

The Elias Sports Bureau said Harper was the first player in history to reach base seven times without an official at-bat.

Things almost became almost comical when Harper strolled to the batter's box. In the 10th inning and again in the 12th, the Cubs intentionally walked him with runners on first and second and two outs. At one point, Harper was kidding with catcher David Ross as four balls sailed wide.

The Cubs escaped both bases-loaded jams by retiring Ryan Zimmerman.

Harper drew three intentional walks in the game.

Baez homered with one out off Blake Treinen (2-1). Baez entered as a pinch hitter, stayed in to play third base and later connected for his second home run of the season.

Travis Wood (1-0) went one inning for the win.

The Cubs won for the 20th straight time when Jake Arrieta started. The NL Cy Young Award winner got a no-decision, giving up two earned runs in five innings.

Kris Bryant hit a tying, two-run single off Nationals reliever Yusmeiro Petit in the seventh.

Arrieta was in line for his first loss since last July 25 — when Philadephia's Cole Hammels pitched a no-hitter at Wrigley Field — before Chicago rallied for its 11th win in 12 games.

The Cubs are off to baseball's best 30-game start since the 1984 Detroit Tigers were 26-4.

Arrieta's ERA increased from 0.84 to 1.13 on a day when struggled with his control. The right-hander lasted just five innings for the second time in three starts.

Arrieta walked four, struck out seven and threw three wild pitches.

Washington's Tanner Roark gave up one run and four hits in six innings. 

TRAINER'S ROOM

Nationals: 2B Daniel Murphy and 3B Anthony Rendon, who have been ill in recent days, were in the lineup.

Cubs: C Miguel Montero (lower back tightness) increased his hitting Sunday, with Maddon saying it went well. He will hit again in the cage Monday and the Cubs will then determine a course of action. Montero is eligible to come off the 15-day DL on Tuesday. ... Dexter Fowler got hit in the right wrist leading off the first but stayed in the game.

UP NEXT

Nationals: RHP Stephen Strasburg (5-0, 2.36 ERA) looks to remain unbeaten as the Nationals open a three-game series against RHP Anibal Sanchez (3-3, 5.87) and the Detroit Tigers.

Cubs: The Cubs send LHP Jon Lester to the mound as they open a three-game series at home against the Padres. RHP Cesar Vargas pitches for San Diego.