SAN DIEGO -- Anthony Rizzo was never a big fan of Petco Park when he was a member of the San Diego Padres.

The first baseman is warming to the downtown facility as a member of the Chicago Cubs.

"I'm starting to enjoy this ballpark," Rizzo said Thursday night after hitting a two-run, go-ahead homer in the Cubs' 5-1 win over the Padres at Petco Park.

The Padres brought in the fences by 10 feet from right to right-center since they traded Rizzo to the Cubs for right-handed pitcher Andrew Cashner on Jan. 6, 2012.

However, Petco Park remains one of the toughest hitters' parks in the major leagues, especially for left-handed batters such as Rizzo.

"This ballpark is still big," Rizzo said. "And it plays bigger at night. It's nice to not have to take batting practice here."

The Cubs trailed 1-0 in the fourth when Rizzo drove a 3-1 pitch from left-hander Eric Stults over the fence in right-center for a two-run homer, his eighth of the season and only his second in 79 at-bats at Petco Park. Rizzo went 2-for-3 with a double in addition to the homer, raising his career batting average at Petco Park to .198.

Rizzo's home run and a three-run rally in the fifth provided more than enough run support for right-handers Arrieta (1-0) and Carlos Villanueva, who teamed to hold the Padres to one run on seven hits and -- as important -- give six members of the Cubs' overworked bullpen the night off.

Before Thursday night's opener to the four-game series, Cubs manager Rick Renteria, a former Padres bench coach, said he wanted to avoid using at least four members of his bullpen.

Renteria was hoping Arrieta could go further than he did in any of his three previous starts since coming off the disabled list May 3 after recovering from a tight shoulder. When Arrieta was done, Villanueva was going to go as far as he could.

"Even if Jake had to come out early, that was the plan," Renteria said.

Arrieta set season highs with six innings and 94 pitches, giving up one run -- a first-inning solo homer by left fielder Seth Smith -- on four hits and a walk.

Villanueva allowed three hits over three shutout innings to record his first save since 2010 and the Cubs' first three-inning save since July 18, 2007.

"We needed Jake and Villanueva to come through, and they did," Renteria said after the Cubs posted their fourth win in five games while extending the Padres' losing streak to four games. "Jake did a nice job. He pushed himself and did a better job of commanding the ball. Other than that one pitch, he did a great job. He worked as efficient as he possibly could."

Arrieta said, "I wanted to get deep into that game and preserve the guys in the bullpen. I used my changeup more than normal because I had good command of it."

Padres catcher Nick Hundley said of Arrieta, "I was impressed. I think I faced him in 2010 when he was with the Orioles, and he's a completely different pitcher now.

"He has a good, hard cutter and backed it up with a fastball. And the curve was an equalizer for him. He threw it for strikes, then threw it out of the zone later in the game."

Rizzo's homer and the three runs the Cubs scored in the fifth all came off Padres left-handed starter Eric Stults, who allowed five runs on six hits in 4 2/3 innings.

Stults (2-5) didn't permit a hit until Cubs left fielder Junior Lake opened the fourth with a perfect bunt single up the third base line. Rizzo followed with his homer run.

The Cubs padded their lead in the fifth. Right fielder Nate Schierholtz pulled a double down the line in right to lead off the inning, and he scored on second baseman Darwin Barney's single to center. Barney came home on a single by center fielder Emilio Bonifacio, who advanced to second on a wild pitch and scored on a double by Lake.

NOTES: San Diego LHP Robbie Erlin was placed on the 15-day disabled list due to elbow soreness. The Padres called the injury similar to the one that landed RHP Andrew Cashner on the 15-day disabled list Saturday. ... RHP Tim Stauffer will make Erlin's scheduled start Friday night against the Cubs. ... San Diego purchased the contract of RHP Blaine Boyer from Triple-A El Paso to replace Erlin. ... Cubs OF Justin Ruggiano, out since April 24 with a left hamstring strain, played nine innings Thursday for Triple-A Iowa and went 1-for-5. He could be close to activation. ... Cubs RHP Hector Rondon got a night off after he worked each of the previous four games.