SAN FRANCISCO -- Paul Clemens felt so under the weather Monday, it reminded him of the time he pitched a junior college game one day after having his wisdom teeth pulled.

He pitched a one-hitter that day for Louisburg (N.C.) College.

The right-hander was nearly as good Monday night against the San Francisco Giants.

In a start interrupted twice by trips to the clubhouse bathroom to throw up, Clemens won for the first time in a month, combining with five San Diego Padres relievers on a five-hit shutout in a 4-0 victory over the Giants.

The loss dropped the Giants (77-66) four games behind the Los Angeles Dodgers (81-62) in the National League West with just 19 to play.

San Francisco retained a 1 1/2-game lead over the New York Mets (76-68) and a two-game edge over the St. Louis Cardinals (75-68) for the NL's two wild-card playoff berths.

Clemens (3-5), who allowed 10 runs over 12 1/3 innings in his past three starts, all losses, checked the Giants on three hits for five innings. He walked one and struck out two in his first career appearance against San Francisco.

It was a start he was determined to make despite a stomach bug. But every inning was an adventure, noted Padres manager Andy Green, who stayed so far away from his starter in the dugout, you would have thought he was pitching a perfect game.

"He fought through a lot today," Green said. "It was a Michael Jordan flu game for him."

For Clemens, it was the first time this season in 11 starts that he allowed fewer than two runs. The 28-year-old's previous win came Aug. 12 against the Mets.

"I feel fine," he said afterward. "Three or four guys hit the ball hard tonight. The ball went my way."

Brandon Morrow, Jose Dominguez, Brad Hand, Ryan Buchter and Brandon Maurer combined for four innings of two-hit relief to cap the Padres' ninth shutout of the season.

Green said he had his bullpen on stand-by basically from the first pitch.

"I'm glad he was able to get through five (innings)," the manager said. "Every inning, we didn't know what we were going to get from him."

Former Giants catcher Hector Sanchez belted a two-run home run, and Yangervis Solarte also collected two RBIs for the Padres, who have won four in a row against the Giants after beginning the season with nine consecutive losses against their California rival.

Sanchez's home run came off Giants starter Jeff Samardzija in the sixth inning. It followed a single by Ryan Schimpf.

"Crazy," Sanchez said of just his third homer at AT&T Park in 119 games. "I never expected the ball to go out, especially the way the ball wasn't flying today."

The home run was his third of the season.

Sanchez had three hits and Luis Sardinas two hits for San Diego, which had lost its previous 11 games in San Francisco.

The Padres out-hit the Giants 9-5.

Hunter Pence continued his hot hitting for the Giants, going 2-for-4. He has 13 hits in his past 18 at-bats.

The Giants, who had a three-game home winning streak snapped, opened a seven-game homestand.

"We've had guys hot and cold since the break. We have not been consistent," Giants manager Bruce Bochy said. "It looked like we came out of it in Arizona. It sure looks bad to get shut out when you get back home the first day."

Samardzija (11-10) gave up four runs on eight hits in six innings. He walked one and struck out six.

Samardzija had the Giants' only extra-base hit of the game, a fifth-inning double, and also one of the club's loudest connections, a 390-foot fly ball to the warning track in center field his first time up.

"Here at night, man, you never know, especially to center. It's kind of a graveyard out there," he said. "I knew I hit it good. But after that, you're just curious to see how it flies. It held up."

For the second day in a row, the Padres went one time through the lineup without getting a hit. However, after their first 10 batters recorded no hits Monday, their next 10 got six, helping produce the game's first two runs.

Sardinas got the ball rolling with a triple to left-center field leading off the fourth against Samardzija. He scored on a single by Solarte.

Alexi Amarista, Jon Jay and Sardinas all singled in the fifth, loading the bases for Solarte, whose fielder's choice made it 2-0.

NOTES: Padres C Hector Sanchez recorded his first three-hit game since May 17, 2014, against the Miami Marlins as a member of the Giants. ... Giants 3B Eduardo Nunez was a late scratch from the starting lineup because of a stiff neck. ... The series opened about five minutes before the San Francisco 49ers kicked off their NFL season about 30 miles down the road in Santa Clara against the Los Angeles Rams. ... Padres CF Travis Jankowski did not make the trip north with the club Sunday night while tending to a private family matter. San Diego manager Andy Green said he expects Jankowski to rejoin the team at some point this week.