SAN FRANCISCO -- There is no panic in Joe Panik.

Nor any of his San Francisco Giants teammates, for that matter.

Facing elimination for the second time in four games this postseason, the Giants stayed alive Monday night when Panik's double off the right field fence scored Brandon Crawford with no outs in the bottom of the 13th inning, delivering a 6-5 win over the Chicago Cubs to force a Game 4 in the best-of-five National League Division Series.

"What they did tonight, that's one of the best, most exciting games I've ever been involved in," Giants manager Bruce Bochy saod shortly after the 5-hour, 4-minute marathon. "The game had everything. It was just a fun game to be involved with."

Still down 2-1 in the series after being swept in Chicago, the Giants will send left-hander Matt Moore to the mound in another potential elimination home game Tuesday night. The Cubs will start right-hander John Lackey.

San Francisco, which captured World Series titles in 2010, '12 and '14, won its 10th consecutive game when facing elimination in the postseason.

"If we're breathing, we're still fighting," Panik said. "I believe in this bunch. Everybody believes in each other, and I think that's why we're able to come back."

Crawford led off the 13th with a two-strike double off the seventh Cubs pitcher, left-hander Mike Montgomery (0-1), who was beginning his fifth inning of relief.

Panik followed with a blast over the head of Cubs right fielder Albert Almora Jr., easily scoring Crawford with the game-winner.

"That ball hung up a little longer than I wanted it to," said Panik, who had a three-hit game. "For me, personally, to win a game like that in the 13th inning for your team when your back's against the wall like that, I know it's definitely up there (with my career highlights). Just the thrill of doing it is pretty special."

Rookie left-hander Ty Blach (1-0) pitched two innings of two-hit shutout relief to get the win for the Giants, who out-hit the Cubs 13-10.

"Good baseball game. That's my takeaway," Cubs manager Joe Maddon said. "I think that both sides should be somewhat exhilarated. Obviously they won, so they're going to feel a bit better about it, but there's nothing on our side to be ashamed of."

Having watched the Giants score three times in the bottom of the eighth inning to take a 5-3 lead, the Cubs rallied into a tie in the top of the ninth on a two-run home run by Kris Bryant off San Francisco closer Sergio Romo.

The homer, which hit the top of the left field fence and bounced into the bleachers, came immediately after Romo walked leadoff hitter Dexter Fowler.

The Giants led all of baseball in blown saves during the regular season with 30.

"I was really proud of our kids, man," Maddon said of the comeback. "I loved our way. We played it hard, we played it right, and they beat us."

San Francisco made a bid for a regulation win when, with Brandon Belt on first base in the bottom of the ninth, Buster Posey hit a liner into the right field corner.

With Belt running from the crack of the bat, Almora made a diving catch to save the game, then doubled Belt off first base to send the game to extra innings.

Posey finished with three hits for the Giants, who recorded the seventh walk-off win in their postseason history.

Denard Span had a double and a triple, and Crawford collected a single and a double for San Francisco.

Bryant had three hits, including his game-tying homer, which was the first for a Cub in the ninth inning of a postseason game since Sammy Sosa did it in Game 1 of the 2003 NL Championship Series against the Florida Marlins.

Javier Baez added two hits for the Chicago.

Cubs standout Aroldis Chapman also blew a save when he was called upon with two on and no outs in the eighth, Chicago clinging to a 3-2 lead.

Conor Gillaspie blasted a two-run, go-ahead triple off Chapman in a three-run uprising that gave the Giants the lead.

On the strength of a three-run home run by starting pitcher Jake Arrieta off Giants ace Madison Bumgarner, the Cubs took a 3-2 lead into the eighth, but then had to call upon Chapman after Belt singled off Travis Wood and Posey drew a walk from Hector Rondon to open the inning.

Chapman, pitching with a lead in the eighth inning for just the fourth time all season, struck out Hunter Pence for the first out, but then served up Gillaspie's triple to right-center field, scoring Belt and Posey with the tying and go-ahead runs.

The hit was just sixth of the season for Gillaspie, a left-handed hitter, against a lefty pitcher. Three went for extra bases.

Chapman never previously allowed a triple to a left-handed hitter.

The big hit was the second of the postseason for Gillaspie, whose three-run homer in the top of the ninth inning produced all the runs in the Giants' 3-0 win over the New York Mets in the NL wild-card game.

Crawford followed Gillaspie's triple with a single through a drawn-in infield to increase the San Francisco lead to 5-3.

The Giants fought an uphill battle from the time Arrieta smacked his homer off Bumgarner in the second inning.

The stunning blow came on a two-strike fastball from Bumgarner, who had never previously allowed a home run to a pitcher in regular-season or postseason play.

It was the first go-ahead, three-run homer by a pitcher in baseball postseason history, and it gave Cubs pitchers six RBIs in the three games against the Giants, tying the record for a postseason series.

Arrieta had two home runs in the regular season, tied for third most in the majors for a pitcher behind Bumgarner and the Mets' Noah Syndergaard (three apiece).

The runs were the first allowed by Bumgarner in the postseason since the ninth inning of Game 1 of the 2014 World Series against the Kansas City Royals, a stretch of 24 innings.

Arrieta, who allowed at least three runs in nine of his previous starts, held the Giants to two in six innings. He gave up six hits and one walk while striking out five.

Bumgarner left for a pinch hitter after laboring through 101 pitches in five innings. He allowed three runs and seven hits, walked one and struck out four.

NOTES: Before 2B Joe Panik's double Monday, the last Giant to record a walk-off hit was 1B/LF Travis Ishikawa, whose home run in the bottom of the ninth inning ended the 2014 National League Championship Series against the St. Louis Cardinals. ... The Cubs fell to 3-5 in their history when they had a chance to close out a postseason opponent. ... The six RBIs in the series by Cubs pitchers ties Chicago with the 1958 Milwaukee Braves (World Series) and 1970 Baltimore Orioles (American League Championship Series) for most in a postseason series. ... The Cubs became the first team since the 1924 New York Giants to have two pitchers hit a home run in the same postseason series. ... Giants LF Angel Pagan (back spasms) was scratched from the starting lineup about an hour before the start of the game. He was replaced by Gregor Blanco. ... In response to Giants CF Gorkys Hernandez's controversial check-swing in the ninth inning of Game 1, commissioner Rob Manfred noted at his pregame press conference that Major League Baseball is likely to continue its policy of not using instant replay to review balls and strikes.