PHILADELPHIA -- Phillies manager Charlie Manuel said it was a must-win situation. His team delivered that victory in dominating fashion.
Howard, the reigning National League MVP, ended a season-high 11-game homerless drought and finished with three hits and three runs scored.
"This was definitely a big win, we've got to keep pushing," Howard said.
The Phillies open another pivotal series on Monday when they host the NL East-leading New York Mets for four games. The team will likely get a lift from second baseman Chase Utley, who is expected to return after missing four weeks with a broken hand.
"I don't like to say make-or-break series, but this one coming up against the Mets is somewhat on the verge of that," Howard said.
San Diego, which led the majors in ERA (3.51) coming into the game, surrendered 14 runs and 17 hits, both season highs. The Padres had won four in a row to move within two games of Arizona in the NL West.
Kyle Kendrick (7-3) pitched six strong innings for the victory. He gave up one run and six hits with a walk and four strikeouts.
"I am surprised at what Kyle has brought to this team," Manuel said. "I didn't realize his composure would be this good."
John Ennis pitched three innings in his Phillies debut for his second major league save.
After Saturday's frustrating 4-3 loss to San Diego, Manuel said that his team "definitely needed to win" on Sunday.
"Yeah, it probably was a must-win game," Werth said. "We'll be OK. There's still plenty of time left in the season, we just couldn't afford to get swept in this series."
Werth is hitting .368 (25-for-68) with three homers and 17 RBI in 23 games since coming off the DL on July 31.
"I haven't played healthy since '04," Werth said. "I'm finally healthy and getting regular playing time. I just want to take advantage of that opportunity."
San Diego's Tim Stauffer (0-1), who was called up earlier in the day from Triple-A Portland to make the start, was roughed up for 11 runs and 11 hits in four innings. Stauffer watched his ERA balloon from 17.18 to 21.13.
"Tim had a tough day," San Diego manager Bud Black said. "It looked like his stuff was fine, but when he needed to record an out, he couldn't make the right pitch."
Philadelphia got off to a fast start as Jimmy Rollins and Tadahito Iguchi opened the game with consecutive singles and Pat Burrell roped a ground-rule double to center. After two strikeouts, Greg Dobbs walked and Werth stroked a two-out, two-run single.
Stauffer ran into control problems in the second, walking Kendrick and Burrell, before Howard launched a two-out, three-run homer to left field. It was Howard's 34th homer and his first since August 12.
"It felt pretty good," Howard said. "I got a good pitch to hit and I didn't miss it."
The Phillies broke the game wide open in the fourth as Aaron Rowand and Werth had RBI singles and Coste connected for his three-run shot -- his fourth of the season -- to make it 11-1.
San Diego finished its road trip 4-2 with a huge four-game home series against NL West-leading Arizona starting on Monday.
"Any time you win two of three on the road, you feel good about yourself," Black said. "But a sweep would have been better."
- Since Citizens Bank Park opened in 2004, the Phillies are 40-11 in Sunday home games.
- Howard is 4-for-5 with two homers and six RBI in his career off Stauffer.
- Werth's five hits were a career-high and he tied his career-high with four RBI.
- The Phillies won the season series 4-3.