SAN FRANCISCO -- San Diego Padres rookie pitcher Jake Smith didn't get the game ball from his first major league win Tuesday night, and he was OK with that.

After all, the most important baseball of the night went home as some bleacher fan's souvenir.

Smith got his win in the most memorable of fashions when fellow rookie Ryan Schimpf belted a two-out, two-strike, three-run home run in the ninth inning, capping a five-run rally that lifted the Padres to a stunning, 6-4 victory over the San Francisco Giants.

"Schrimpfy did all the work. All I did was throw up a zero," said Smith, who was making his second major league appearance after getting called up from Double-A last week. "This was everything I dreamed of."

And it was a nightmare for the Giants (77-67), whose second consecutive loss prevented them from gaining ground on the Los Angeles Dodgers (81-63) in the National League West race.

San Francisco remains four games behind with 18 to play, and now leads the New York Mets (77-68) by just a half-game for the top NL wild-card spot.

"That was tough," Giants manager Bruce Bochy said. "Like a punch in the stomach."

Home runs by Angel Pagan and Gorkys Hernandez helped the Giants take a 4-1 lead into the ninth.

However, the fifth Giants pitcher, Hunter Strickland, gave up three singles and a bases-loaded walk to Wil Myers with one out, allowing the Padres to creep within 4-2.

Strickland got Yangervis Solarte to ground out, scoring Jon Jay, before rookie left-hander Steven Okert was summoned from the bullpen to face the lefty-hitting Schimpf.

"In a situation like that," said Schimpf, a former minor league free agent, "you really don't have time to think (about who's pitching). At the end of the day, it's still a baseball coming at you."

Seeking his first career save, Okert got his rival in a 1-2 hole before Schimpf unloaded on the potentially game-ending pitch, launching it into the bleachers in right-center field for a three-run homer and a 6-4 lead.

"Pretty special," said Schimpf, whose homer was his 19th of the season. "I was just trying to hang tough and not be the last out."

Schimpf ranks third in homers among major league rookies.

Kevin Quackenbush pitched a 1-2-3 bottom of the ninth to record his second save.

Smith (1-0) pitched a scoreless eighth inning.

"We've had a lot of dramatics in late innings," Smith said. "We don't quit."

Strickland (3-3), charged with four of the five runs in the ninth, took the loss.

"He was pitching well," Bochy said of Strickland, who nearly snared what might have been a double-play grounder on Solarte's at-bat that could have ended the game. "I went for the matchup (lefty on lefty), and it just didn't work out. (Okert) got ahead, but then threw one right down the middle."

Jay collected three hits, and Schimpf, Luis Sardinas and Derek Norris had two apiece for the Padres, who have won five straight against the Giants, including a 4-0 decision Monday in the series opener.

The Padres had 12 hits, the first 11 of which were singles.

Hernandez had three hits, including his homer, as the Giants lost to the Padres for just the second time in the past 13 meetings at AT&T Park.

The Giants also had 12 hits but stranded 12 baserunners, including six in scoring position.

San Francisco starter Albert Suarez, seeking his first win since June 23, allowed just one run on six hits in five innings. He walked two and struck out one.

Pagan, Buster Posey and Ehire Adrianza had two hits apiece, and Kelby Tomlinson scored twice for the Giants.

San Diego starter Clayton Richard allowed 11 hits and three walks in 5 2/3 innings. He struck out four and managed to hold the Giants to three runs.

The Giants had six hits, but just one run, against Richard until Pagan's homer triggered a two-run fifth inning that produced a 3-1 lead. It was his career-high-tying 11th of the season.

NOTES: 2B Ryan Schimpf's go-ahead homer with two outs in the ninth was the Padres' second of the season. 1B Wil Myers had one on June 10 against the Cincinnati Reds. ... The Giants have blown six of their 10 save opportunities in September. ... San Francisco 3B Eduardo Nunez (sore back) sat out for the second night in a row. ... Giants RHP Derek Law (strained right elbow) threw a bullpen session before the game, after which manager Bruce Bochy said he would be reinstated from the disabled list for Wednesday's series finale. ... The Padres' Triple-A affiliate, El Paso, began the best-of-five Pacific Coast League championship series Tuesday night with a 7-5 win over the Dodgers' Oklahoma City club.