CHICAGO -- Jake Arrieta's goal may be perfection but he realizes he can occasionally ease up and still have good outcomes.

Arrieta (18-7) scattered five hits in a seven-inning shutout effort as the Chicago Cubs beat the St. Louis Cardinals 5-0 on Friday at Wrigley Field.

Chicago (98-55) topped last year's 97-win total and matched the most victories by any Cubs team since 1945 with its fourth straight in the opener of a three-game weekend series.

The Cubs also clinched home-field advantage throughout the National League playoffs, thanks to the Washington Nationals' loss to the Pittsburgh Pirates Friday night.

"I had several outs today where I took my foot off the gas and I was at about 60-70 percent," said Arrieta, who walked one and struck out 10. "Those kind of moments show me that I don't have to be at 100 percent. I can be at 75-80 percent, execute pitches at the bottom of the zone and make those guys put the ball in play and let our defense work."

The Cardinals (80-73) are one-half game behind the San Francisco Giants for the second wild-card spot.

Arrieta, the reigning NL Cy Young Award winner, captured his 40th victory over the past two seasons.

"That was more reminiscent of what we saw last year," said Cubs manager Joe Maddon. "Not 100 percent there, but that was pretty darn good. ... That lineup that they threw out against us today was a great test to see where he's at."

Cardinals starter Mike Leake (9-11) lasted just 3 1/3 innings and took the loss, his third of the season against the Cubs.

Cubs reliever Pedro Strop was activated off the disabled list (left meniscus tear) on Friday and made his first appearance since Aug. 10. He allowed one base runner and struck out one in a scoreless eighth.

"We definitely wanted to get him in the game today," said Maddon. "He told me afterwards he felt really good. Of course he's going to be a little bit (nervous) in the beginning. You haven't been out there in a while. But once he settled in and the slider became his pitch again then all of a sudden he felt at home."

Anthony Rizzo went 3-for-5 with an RBI while Kris Bryant had two hits and walked once.

Arrieta struck out the side in the first and was given a big lead with four runs in Chicago's half of the inning. Leake struggled right off the bat as five straight Cubs reached base.

Dexter Fowler walked, reached third on Bryant's single to left and scored on a Leake's wild pitch. Rizzo's 41st double of the season, aided by left fielder Kolton Wong's slip on loose turf, brought home Bryant for a 2-0 lead. Rizzo moved to third on another Leake wild pitch and scored on Ben Zobrist's base hit to right.

Jason Heyward reached after grounding into a fielder's choice and scored on Chris Coghlan's double to right to make it 4-0.

"Those have been the kind of innings that have hurt him this year," said Cardinals manager Mike Matheny of Leake. "When he's able to stay away from big innings, you seem him in there pretty deep into the game. That one's tough to bounce back from on a club like this."

The Cubs had the bases loaded in the third with two out, but Miguel Montero struck out to end that threat.

Leake departed with one out in the fourth after giving up hits to Arrieta and Bryant. He allowed five runs on seven hits while walking three and striking out one.

Reliever Dean Kiekhefer faced one batter and loaded the bases with a single to Rizzo. Zobrist then made it 5-0 when he reached base on a fielder's choice and scored Arrieta.

The Cardinals managed just five hits against four Cubs pitchers.

NOTES: Cardinals LF Matt Holliday took live batting practice on Friday and may still see game action in the season's final days. Holliday has been on the disabled list since Aug. 12 with a right thumb fracture and has missed 37 games. ... After wrapping up on Sunday in Chicago, the Cardinals return home for the final seven games of the season -- four games against Cincinnati and three against Pittsburgh. ... St. Louis sends RHP Alex Reyes (3-1, 1.03 ERA) against Chicago RHP Jason Hammel (15-9, 3.56 ERA) in Saturday's middle game. ... Cubs LHP Jon Lester (18-4) is tied for the NL lead in victories and closes the series on Sunday. He is just the third Cubs pitcher since 1893 to allow two or fewer runs and two or fewer walks in each of his last 10 starts. ... The Cubs are on track for 103 victories with nine games to play after Friday's opener. ... The Cubs activated RHP Pedro Strop (left meniscus tear) off of the 15-day disabled list prior to Friday's game and he was available for action.