OAKLAND — It took Jeff Samardzija six starts to get 13 runs of support from the Chicago Cubs at the outset of the season, and he only got 41 runs total in 17 starts before he finally was freed from Windy City bat-less bondage.

So to see that many runs on the board in one day — and 24 in just four starts with Oakland — it’s little wonder that Samardzija has made a quick, happy adjustment to his new surroundings.

“I’ll tell you what, it’s a lot of fun playing here,” Samardzija said after the A’s, led by Brandon Moss’ third grand slam of the season, hammered the Houston Astros 13-1 before 22,759 at the Coliseum on Thursday afternoon. “I just really look forward to coming to the yard every day.”

“It crossed my mind when was the last time he had a lead like this,” said manager Bob Melvin after the A’s had a 4-1 lead even before a five-run sixth inning that included the Moss grand slam.

The tall right-hander responded in kind on the mound, pitching eight innings of four-hit ball. He didn’t walk a batter, struck out six and the only blemish on his line was a solo homer to former Athletic Chris Carter in the fourth inning.

Samardzija mixed his pitches with power and precision, and he left an exclamation point in concluding his day — a 96-mph heater that struck out Jose Altuve, who whiffed three times against Samardzija.

The thing about Samardzija is that he pitches like it’s a one-run game even when he’s got a big lead. But he admitted that runs always help focus his aggressiveness.

“I was just attacking the zone,” he said. “That’s what run support will do for you. It gets you calmed down. I like to throw a lot of fastballs so when you get a lead like that you can really pound the zone, get ahead in the count, and go from there.”

The other thing Samardzija was proud of was giving the bullpen a much-needed blow. He happened to see Melvin’s postgame media session on TV at his hotel Wednesday night when the manager was asked what his relief corps was looking like for Thursday and Melvin replied, “Samardzija.”

“I was thinking, ‘All right, well I better get to bed, and get ready,’ ” the pitcher said. “It was pretty cool to hear that. I love it when people put some pressure on you and expect a lot out of you. It makes you really want to come to the park ready to pitch and do your job, and pick those guys up.”

As for Moss, he became the first A’s player to hit three grand slams in a season since Miguel Tejada in 2001, and he has 61 more games to go after Jason Giambi’s club record of four set in 2000.

“I’ve had quite a few at-bats with the bases loaded this year,” he said. “When you get in that situation and a guy has to make a pitch, you can be aggressive. ”