PEORIA, Ariz. (AP) — Buster Posey hit a grand slam and the San Francisco Giants rocked opening day starter Andrew Cashner, rolling to an 11-3 victory Thursday night over the San Diego Padres.

Madison Bumgarner, set to start the Giants’ opener March 31 at Arizona, gave up five hits in seven scoreless innings. The left-hander struck out nine in his fifth Cactus League start and hasn’t allowed a run in 17 innings this spring.

“Geez, I don’t know what’s going on,” Bumgarner said. “I feel good. This is by far the best spring I’ve had numbers-wise. Tonight I felt pretty close to ready. I’m happy, real happy, with it.”

Cashner was tagged for eight runs — four earned — and nine hits in 3 2/3 innings. He threw 94 pitches, 63 strikes, in his fourth spring training start.

The right-hander had not given up a run in nine prior innings of work this spring.

Before the game, Padres manager Bud Black announced that Cashner will pitch the season opener March 30 against the Los Angeles Dodgers at Petco Park.

“Minus the grand slam, I thought I pitched pretty well,” Cashner said. “I left my fastball high up in the zone a lot today. That’s how the grand slam happened. It was a fastball, high and right down the middle.

“But I threw some good changeups today. My sinker was just not there. I just think I need to put it all together in one game.”

Cashner was encouraged by his pitch count.

“It’s just a real good sign that I’ll be ready,” said Cashner, who was 10-9 with 3.09 ERA last season.

STARTING TIME

Giants: Bumgarner threw 97 pitches, 67 strikes. If he made a mistake, it was trying to lay down a bunt against Cashner, whose fastball has been known to hit 100 mph. Bumgarner struck out.

“He’s not the easiest pitcher to bunt an, especially on your first try in spring,” Bumgarner said. “I mean, he throws 9,000 mph.”

Padres: The 27-year-old Cashner will be making his first opening day start. “His development in so many different areas over the last 12 months leads us to believe that he can be a guy out in front of a rotation, a guy who can do great things,” said Black, who told Cashner he had the assignment a few days ago.

TRAINERS’ ROOM

Giants: Marco Scutaro’s back continued to trouble him, casting doubt on whether he’ll be at second base on opening day. After making his first spring start Monday, Scutaro received an epidural shot Thursday in an attempt to alleviate inflammation. Scutaro’s chances of starting the opener are “50-50,” manager Bruce Bochy said. Joaquin Arias was at second Thursday night and will start on opening day if Scutaro can’t. ... Outfielder Michael Morse played six innings in a minor league game. He has been nursing a mild strain to his right calf. He hopes to be back in the lineup Friday against the Oakland A’s.

Padres: First baseman Yonder Alonso didn’t play. He’s been battling the flu. He hopes to be back in the lineup Friday against Seattle. ... Outfielder Alex Dickerson left camp to have his injured left ankle examined by team physicians in San Diego. A bad sprain has sidelined him indefinitely.