SAN FRANCISCO -- Every team is bound to experience its peaks and valleys over the course of a season. The Giants are picking an inopportune time to go through one of those lulls.

The Giants’ recent offensive struggles continued in a 6-2 loss to the Brewers on Tuesday night at Oracle Park. San Francisco has lost four of its past five games and scored only three runs over its past three games. And after the latest defeat, manager Gabe Kapler didn’t mince words.

• Box score

“Hasn’t been our best baseball and we have to play better,” Kapler said. 

Giants starter Johnny Cueto wasn’t sharp, allowing six earned runs on 10 hits in 3 2/3 innings after he was scratched on Monday, when he experienced cold and flu-like symptoms and received an IV that night. He began feeling ill on Sunday as the team was traveling back from Atlanta and was placed on the COVID-19 injured list, although he did not test positive.

“I don’t feel so great, but that’s not an excuse,” Cueto said.

There were some individual moments that were positives for the Giants on this night.

Most notably, Brandon Belt hit his 20th home run of the season -- a solo shot in the sixth inning -- marking the first time in his career that he’s hit that many in a season. He had come close to that number in the past, hitting 17 (2013, '16 and '19) or 18 (2015 and '17) home runs five times.

Not to be lost in the shuffle was left-hander José Quintana. After being claimed off waivers from the Angels on Monday, Quintana pitched 3 1/3 innings of scoreless relief with six strikeouts, providing some much-needed length the day after a bullpen game. Quintana had a called-strike-plus-whiff rate of 41.6 percent, his best in 25 outings this season.

Along with his dominance on the mound, Quintana smacked an opposite-field single in his first plate appearance of the season in the fifth, bringing a crowd that was waiting to cheer to its feet.

“That looks like the version of Quintana that I’ve seen when he looks really good over the years,” Kapler said. “He’s able to execute his breaking balls, fastball had good life and good carry. He was throwing a lot of strikes, and as he has all year long, he’s missed bats.”

The efforts from Belt and Quintana made for momentary jubilation, but there wasn’t much for the home crowd to cheer about otherwise.

Milwaukee raced out to a six-run lead, scoring two in the first, one in the second, two in the third and one in the fourth. With right-hander Brandon Woodruff, one of the Brewers' three National League Cy Young Award candidates, on the mound, the Giants quickly found themselves in a tough hole.

The fourth was an especially trying affair, featuring several blunders in the span of two pitches. Third baseman Kris Bryant and left fielder Alex Dickerson converged on Omar Narváez’s weakly hit popup, but neither could make the catch, allowing Christian Yelich to score from first base. To compound matters, Cueto threw the ball into foul territory trying to nab Narváez at first, allowing him to advance to second.

On Cueto’s next pitch, Bryant lunged to his right to stop Avisaíl García’s sharply-hit grounder, but his throw was well wide of the bag. It was ruled an infield single, but it was emblematic of San Francisco’s defensive struggles.

“Tonight’s defensive effort wasn’t strong enough,” Kapler said. “I think we all know that. In particular, I think Johnny needed us to play really good defense behind him to give him a chance to go deeper into the game, and we weren’t able to do that.”

San Francisco now finds itself in danger of losing its grasp on the NL West. Los Angeles beat Atlanta, 3-2, shrinking the Giants’ division lead to a half-game. Should the Giants lose and the Dodgers win on Wednesday, San Francisco will be out of first for the first time since May 30.

The Giants have consistently gone toe-to-toe against some of the best teams in baseball, including these Brewers. If they want to come out of this week still atop the West, they’ll need to find some answers fast.