SAN DIEGO -- Going into Sunday afternoon at Petco Park, right-hander Jerome Williams had one of the worst road records in the long history of the Philadelphia Phillies.

In his first nine road starts this season, Williams was 0-6 with an 8.02 earned-run average. The last Phillie to lose at least six games on the road with an ERA over 8.00 was Les Sweetland, who was 2-10 with an 8.02 ERA -- back in 1930.

But on Sunday, the 33-year-old Williams reversed his road woes by allowing the Padres one run on five hits with two strikeouts over seven innings to pick up the win as the Phillies completed a three-game sweep at Petco Park with a 5-3 win.

"That is the best we've seen Jerome all year," said interim manager Pete Mackanin, as the Phillies' third straight win in San Diego ran their post All-Star record to a major league-best 16-5.

"He kept the ball down in the zone. He did a real nice job. He changed speeds real well. I'm very happy about that."

"I just stuck to the plan," said Williams. "If I consciously keep the ball down, I get my ground balls."

Williams got eight ground-ball outs, including six straight ground outs between the third and fifth innings, while improving to 4-8 and lowering his earned-run average from 6.09 to 5.73. Williams, 33, is one of 12 active major league pitchers to have also made a start at Qualcomm Stadium before Petco Park opened in 2004.

Offensively, the Phillies got a two-run, pinch-hit double from Chase Utley in the top of eighth to make it 5-1.

Earlier, center fielder Odubel Herrera hit a solo homer off Andrew Cashner (4-12) while first baseman Ryan Howard and second baseman Cesar Hernandez had run-scoring hits off the Padres' right-handed starter.

"Cashner pitched great," said Padres interim manager Pat Murphy. "He pitched on the edges and changed speeds."

"We played some good baseball for a while and now we're scuffling a bit," Cashner said of the Padres, who have lost six straight following a 13-5 run.

Murphy used the term "snake bit" when he discussed the Padres' plight. "The Phillies are playing great. We're pressing a little bit and getting into a rut. We're not that far off."

The only run allowed by Williams came on a sixth-inning solo homer by Justin Upton. Right-hander Ken Giles picked up his third save of the series and his sixth in as many tries since taking over the closer role after Jonathan Papelbon was traded to Washington.

The Phillies struck quickly for a run in the first, continuing a troublesome trend for the Padres. The Padres have given up first-inning runs in three of their last four games, seven of the last nine and nine of the last 13.

Hernandez opened with a single and moved to second on Herrera's single. Hernandez scored on Howard's double to right with Herrera holding at third. Cashner avoided further dame by striking out right fielder Jeff Francoeur and retiring left fielder Cody Asche on a fly to left.

After Cashner finished a run of retiring 15 of 16 Phillies, Herrera led off the sixth with his sixth homer of the season -- a 425-foot drive to right.

Williams had allowed the Padres' only three hits, including a bunt single by Cashner, and four baserunners through 5 2/3 innings before left fielder Upton put the hosts on the board with a 421-foot homer into the second deck in left.

But the Phillies padded their lead against Cashner and the Padres bullpen in the top of the seventh.

Shortstop Freddy Galvis and catcher Carlos Ruiz opened the inning with back-to-back singles putting runners at the corners with no one out. Williams bunted Ruiz to second with Galvis holding at third.

Right-handed reliever Brandon Maurer replaced Cashner and was greeted by Hernandez, who ripped a single off the glove of second baseman Jedd Gyorko, who was playing in on the infield grass, for a RBI single.

Left-handed specialist Marc Rzepcynski struck out left-handed Phillies Herrera and Howard around an intentional, base-loading walk to third baseman Maikel Franco to keep the score at 3-1.

Asche saved Williams and the Phillies a run with one out in the bottom of the seventh when he jumped at the wall in left to rob Padres catcher Derek Norris of a solo homer.

The Phillies increased their advantage to 5-1 in the top of the eighth on Utley's two-run double.

The Padres scored single runs in the eighth and ninth on RBI singles by third baseman Yangervis Solarte and center fielder Will Venable, who finished with three hits.

NOTES: RHP Colin Rea will be promoted from Triple-A El Paso to make his major league debut Tuesday night against the Reds at Petco Park. Rea is a combined 5-4 with a 1.95 ERA over 101 2/3 innings this season at Double-A and Triple-A. ... When Rea moves into the rotation, RHP Odridsamer Despaigne will move to the bullpen and the Padres while also likely add a fifth player to the bench while reducing the bullpen by two. ... Phillies CF Odubel Herrera extended his hitting streak to 12 straight games with his first-inning single Sunday.