Padres need a sweep in San Francisco to play on

Reporting from San Francisco

There’s little mystery about the challenge facing the San Diego Padres here this weekend: Sweep their three-game series with the San Francisco Giants and they still have a chance for a division title.

But lose just once and they go home.

The red-hot Giants pushed the Padres to the brink of elimination Thursday, riding three home runs to a 4-1 win over Arizona while the struggling Padres were managing just three hits in being shut out, 1-0, by the Chicago Cubs.

That combination gives the Giants a three-game lead in the National League West race with three games to play. The Padres haven’t been that far out of first since mid-April.

San Diego’s loss also boosts idle Atlanta’s lead in the wild-card standings to two games over the Padres, dropping the Braves’ magic number in that race to two.

“We’re not done,” Padres outfielder Ryan Ludwick told reporters in the San Diego clubhouse. “Everyone in here knows it’s not going to be easy, but it’s not impossible.”

Added first baseman Adrian Gonzalez: “We’ve got to find a way to be very good for three days. That’s all it takes.”

For San Diego, which led the division race as recently as five days ago, Thursday’s loss was its fourth in five games — and the Padres have scored just seven runs over that span. The Giants, meanwhile, have won eight of their last 10, erasing what was a second-half-high 6½-game deficit to San Diego just five weeks ago.

“It’s a good feeling. We’re in a good position,” Giants catcher Buster Posey told reporters after following solo home runs by Pablo Sandoval and Andres Torres with a two-run shot of his own. “You can’t really take anything for granted. We all know baseball’s a crazy game, so we’ve got to come out and stay focused.”

In the American League, the slumping Tampa Bay Rays lost to Kansas City, 3-2, dropping into a first-place tie with the idle New York Yankees in the East Division with three games left. The loser of that race still will advance to the playoffs as the league’s wild-card team.

kevin.baxter@latimes.com