CHICAGO -- The Giants’ horrid start to September took another turn for the worse on Tuesday night.

San Francisco’s struggling offense came alive for four home runs, but it wasn’t enough to overcome shoddy pitching and defense, which cost the Giants two leads in a demoralizing 11-8 loss to the Cubs at Wrigley Field.

J.D. Davis put San Francisco ahead, 6-4, with a two-run shot off Chicago reliever Hayden Wesneski in the sixth inning, but the Cubs rallied back in a six-run seventh that featured a game-tying two-run homer by Seiya Suzuki and a back-breaking three-run blast by Christopher Morel.

“It’s definitely frustrating,” Davis said. “Going through this spurt that we’re in right now of not producing as an offense, and then to turn it around and have an offensive day like this and for them to be tough at-bats, tough outs, pesky at-bats … This one definitely stings.”

With their fifth straight loss, the Giants remain winless in September and have now dropped eight consecutive series on the road. Their playoff odds have plummeted from 80.4 percent on Aug. 4 to 26.9 percent, their lowest mark since April 22, according to FanGraphs.

• Games remaining (23): at CHC (1), vs. COL (3), vs. CLE (3), at COL (4), at AZ (2), at LAD (4), vs. SD (3), vs. LAD (3)

• Standings update: The Giants (70-69) slipped two games behind the Reds (73-68), 1 1/2 games behind the Marlins (71-67) and one game behind the D-backs (71-68) for the third and final National League Wild Card spot. San Francisco also fell five games behind the Cubs (75-64) for the second NL Wild Card position. Chicago has won the season series by taking four out of the first five games, securing the head-to-head tiebreaker in the standings.

Suzuki ignited the Cubs’ decisive rally by launching a hanging slider from submariner Tyler Rogers into the left-field bleachers to tie the game at 6 in the seventh, and Chicago kept adding on with the help of a defensive miscue by left fielder Joc Pederson, who allowed a routine fly ball off the bat of Jeimer Candelario to fall for a one-out double.

“I messed it up,” Pederson said. “It’s frustrating when you’re scraping, grinding, trying to win games, trying to get into the playoffs. I let the team down, for sure. That play lost us the game. It doesn’t feel good.”

Candelario advanced to third on an infield single by Yan Gomes and then scored the go-ahead run on an error by third baseman Casey Schmitt, who fielded Nick Madrigal’s chopper but made a one-hop throw to the plate that skipped past catcher Patrick Bailey. To make matters worse, Bailey -- who had entered the game as a defensive replacement for Blake Sabol -- suffered a possible concussion on the play, prompting the Giants to lift him in favor of pinch-hitter Paul DeJong in the top of the ninth.

Things continued to unravel for the Giants, who absorbed another gut-punch after Morel crushed a three-run shot off Luke Jackson to cap the Cubs’ six-run outburst.

“Obviously, you can’t give away extra outs against a team that’s going to the playoffs,” manager Gabe Kapler said. “The Cubs are playing good baseball right now. You can’t give them additional outs, or they’re going to punish you for it.”

The Giants squandered an encouraging performance from their offense, which had been shut out in back-to-back games but came back to seize an early 3-0 lead behind homers from LaMonte Wade Jr. and Mike Yastrzemski. Still, the Cubs erased the deficit by scoring four runs in the third against relievers Scott Alexander and Jakob Junis.

Nico Hoerner opened the inning by legging out an infield single on a grounder to Davis, who took an extra shuffle before firing to Wade at first base. Hoerner later scored on Dansby Swanson’s RBI single to put Chicago on the board. Junis also missed a chance to turn a potential inning-ending double play on Suzuki’s one-out comebacker, letting it go in the hopes that the Giants’ defense would be able to make a play behind him.

Thairo Estrada managed to backhand the ball and prevent it from rolling into the outfield, but he couldn’t record an out on the play, extending the inning for Chicago. Junis then issued a bases-loaded walk to Candelario and surrendered a two-run double to Gomes that got past a diving Pederson in left field, giving the Cubs a 4-3 lead.

“We win as a team, we lose as a team,” Kapler said. “Right now, it just seems like we’re not doing the thing that we need to do to finish a team off or win a baseball game.”