Heyward drives in all 3 runs for Cubs, including winner in 13th

The magic number for Cubs manager Joe Maddon is always 1.

Even as his team moves closer to clinching a playoff spot as the likely Central champ, the game of the day is the most important.

That’s true even if the Cubs aren’t facing a potential playoff opponent such as the San Francisco Giants, who are in their own fight to reach the postseason.

“You have to stay mentally focused to the last drop,” Maddon said.

The last drop Sunday didn’t come until the 13th inning, when the hitting hero of the day, Jason Heyward, singled home Anthony Rizzo for a 3-2 victory.

“My take is we have the lead we do because we’ve played [all season] the way we did [against the Giants],” Maddon said of taking three out of four. “Nobody is mailing anything in. Nobody’s taking anything for granted. We’re taking it one game at a time.”

There were many heroes in the series finale. Starter Jason Lackey allowed two hits in five innings in his return from the disabled list. Seven relievers held the Giants to two hits, with Trevor Cahill (4-4) getting the win.

But the man wearing the brightest badge was Heyward, who has had a hard-luck season at the plate.

After his second error of the season led to an unearned run in the second inning, Heyward drove in all three runs for the Cubs.

“It feels good to help,” he said of his 3-for-6 day and first walk-off hit since Aug. 18, 2010. “The error [dropping Hunter Pence’s fly ball] stayed with me about a second, but seeing how the wind was playing, I just overran it. It happens. You keep playing, and you have to keep being a part of the game.”

Lackey shook off the miscue and Heyward’s apology.

“He’s played Gold Glove defense all year,” Lackey said. “I’ll take that guy out there every day of the week.”

Lackey didn’t allow a hit until the fifth, a double by Eduardo Nunez that turned into the Giants’ other run.

With the Cubs trailing 2-1 in the ninth, Addison Russell led off with a double and scored on Heyward’s single. Heyward also drove in Rizzo in the fourth.

“Sometimes you’ll hit it where they’re at, and sometimes they’re playing you where you hit it,’’ Heyward said of his off year at the plate. “It’s one day at a time, and you keep competing and try to do something every day to help the team win.”

The four-game series was akin to playoff baseball, with each game decided by one run. Cubs pitching allowed only 14 hits in the series, tying a franchise record for fewest allowed in a four-game set, the last time coming in August 1934 against the New York Giants.

Yet the Giants were in every game, despite hitting .108 in the series.

“They played great defense, too,” Maddon said. “It was really passionate on both sides.”

If the Cubs face the Giants again, Maddon believes they could pose a greater challenge.

“If the Giants have any shortcomings now, you know they’ll improve on them,” he said. “They have a nicely balanced, professional group. Whatever is wrong now, heads up —it won’t be wrong at the end of the season.”

The Giants must first get to the postseason, either by overtaking the Los Angeles Dodgers for the West title or as a wild-card team.

The Cubs, meanwhile, lowered their real magic number to 11.

And there’s no letting up on the gas, Maddon said.

“We’re coming to play every day, playing the same game,” he said.

“It’s an exciting time for us,” Heyward said. “We don’t take anything for granted.”

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