There already have been eight decided by one run, and five others by two runs.
Wade Miley hit his first career home run, Eric Chavez connected and Cody Ross added a two-run single against the team he helped win the 2010 World Series, yet Arizona couldn't hold a late lead in losing 5-4 to the San Francisco Giants on Monday night.
Brandon Belt singled to left-center with one out in the ninth and Buster Posey tied it with a two-run homer in the eighth of San Francisco's seventh straight home victory.
"It was a ballgame we should have won," Arizona manager Kirk Gibson said. "Obviously it's disappointing. We got a good start from Wade, played a good ballgame and we couldn't close them out. They've had several come-from-behind wins. We got in a bad situation and made a bad pitch and got beat by a very good guy, the one guy you don't want to beat you ended up tying the game up."
Belt's first career walkoff hit came against Tony Sipp (1-1), who allowed a leadoff single to Andres Torres. Brandon Crawford sacrificed him to second. Belt was mobbed by his teammates afterward.
"I'm pretty lightheaded and my kidneys hurt right now," he said. "Somebody got me."
Posey's drive to straightaway center was his second homer of the year and in as many days.
Jose Mijares struck out two in the ninth before yielding Cliff Pennington's double. Closer Sergio Romo (1-1) relieved in a double switch as Belt entered at first base. Romo retired pinch-hitter Eric Hinske on a first-pitch grounder.
Arizona played its third straight one-run game, and has lost two of those.
"It's not the way you want to end it," said Chavez, who hit career homer No. 250. "We do a lot of what they did tonight when we're down, so we've got to find a way to close the door when we have the lead. We put together really good at-bats late in innings like they did tonight."
Miley crushed a 2-0 pitch deep into the right field arcade in the fifth off Ryan Vogelsgong—and the ball was thrown back onto the field, so the pitcher might have a souvenir to take home. Ross threw his right arm into the air to cheer his teammate.
In the sixth, Ross drew cheers with a sensational diving catch near the foul line in right field to rob Posey of a likely extra-base hit. Ross then got to his knees and quickly threw to the infield as shortstop Didi Gregorius clapped.
The Giants gave up home runs to a third different pitcher this month, the first time they had done so in the same calendar month since June 1953. Clayton Kershaw of the Dodgers and Milwaukee's Yovani Gallardo also connected against the Giants.
Vogelsong has allowed one homer in three of his four starts and each of his last three. The right-hander was tagged for two homers in a game for the first time since allowing three to Atlanta on Aug. 24 last year, the only time he did so in 2012.
"There's no quit in this team, I can tell you that," Vogelsong said. "We fight 'til the last out. It's pretty fun to watch."
He loaded the bases on just 12 pitches to start the game—back-to-back singles by Gerardo Parra and Martin Prado followed by a seven-pitch walk to Paul Goldschmidt before Ross' bloop single that went past leaping second baseman Marco Scutaro.
That hit by Ross, the 2010 NL championship series MVP for the Giants, ended a stretch of 21 shutout innings by San Francisco's pitchers after consecutive shutouts in a weekend sweep of the Padres. It was the longest scoreless streak by the club since 36 innings from June 25-29 of last year.
The Giants added those two runs right back in the bottom half with three straight one-out doubles, including those by Pablo Sandoval and Posey to drive in runs after Scutaro got things started.
Goldschmidt walked in his first two plate appearances then was hit by a pitch in the fifth.
Miley struck out seven and didn't walk a batter but remains winless in three career starts and four total outings against the Giants.
At the plate, Miley was 0 for 5 this season and 12 for 83 lifetime (.145) with a pair of doubles before the homer. His hit snapped an 0-for-36 funk by D-backs pitchers dating to Trevor Cahill's single on Sept. 29 last year against the Cubs.
"They put together a good inning late," Miley said. "It just slipped away from us."
San Francisco athletic trainer Dave Groeschner and Bochy checked on Posey in the top of the second after a bouncing pitch hit him in the right side of his neck. The reigning NL MVP and batting champion stayed in the game and said afterward he was fine.
Posey sure looked it on the home run.
"He's some kind of special," Vogelsong said.
Monday's game kicked off the first of 19 between the rivals who were an even 18-18 in their matchups the past two years.
NOTES: Parra had two of Arizona's nine hits. ... Ross hadn't been back to AT&T Park since signing with Boston before the 2012 season. Even while playing for division rival Arizona, the bearded, smiling Ross is still a beloved figure in San Francisco. "This place will always have a special place in my heart," Ross said.