ST. LOUIS -- It was a more aggressive Luke Weaver that toed the mound Friday night in Busch Stadium. He didn't nibble at corners and give too much credit to hitters.

Because he attacked more and minimized mistakes, Weaver is now the owner of his first major league win.

Going six innings for the first time in his three big league starts, Weaver led the St. Louis Cardinals to a 3-1 decision over the Oakland Athletics.

Weaver gave up four hits and a run, walking two and striking out seven. Aside from a bad first-pitch changeup that Yonder Alonso walloped over the right-center field wall in the second for his seventh homer, Weaver (1-1) controlled most of the counts and fetched eight groundouts.

"Just trusting myself," Weaver said when asked to identify the biggest difference in this start and the first two. "Everything just felt better. The ball was coming out of my hand better and I could put it where I wanted to."

Pitching at home for the first time in the majors seemed to agree with Weaver, who slipped five called third strikes by Oakland hitters.

"Today was a great step in the right direction," St. Louis manager Mike Matheny said of Weaver. "It was nice to see him get through the first without a lot of traffic and not have to pitch under stress right away. He just continues to get better every start."

Weaver set a quick tone with two strikeouts in a 1-2-3 first and then pitched from the lead for the outing's remainder after Jedd Gyorko extended the Cardinals' home run streak to 15 games with a two-run blast to center field in the inning's bottom off Ross Detwiler (1-3).

The 423-foot shot was Gyorko's 15th since the All-Star break, tops in the National League, and moved him within one of his career high, set as a rookie in 2013 with San Diego.

"I got a pitch I was looking for, a changeup, and put a good swing on it," Gyorko said. "Other than that, (Detwiler) was good. We didn't put a whole lot of good swings on him."

A product of Wentzville, Mo., about 30 miles west of St. Louis, Detwiler retired 13 of the next 15 men he faced and matched Weaver pitch-for-pitch after Gyorko's blast. But the Cardinals did manage to scratch out an insurance run off him and reliever Ryan Dull with the help of good baserunning, unusual for a team which has led MLB in making outs on the bases.

With one out in the sixth and Brandon Moss at first, Yadier Molina looped a single to short center that moved Moss to third as he got a good read on the ball. Dull came in and induced a short fly ball to center from Jhonny Peralta for the second out.

Moss tagged up and appeared to be quicker than Coco Crisp's accurate but not strong throw. Molina made sure that Moss would score by trying to advance to second, ultimately inviting a rundown that traded an out for the game's last run.

"Those were a couple of huge baserunning plays from guys not known as basestealers," Matheny said. "Moss got a good read on that looper, and Yadi was very heads-up to get into that rundown, knowing how important that run was."

Detwiler allowed six hits and three runs in his 5 1/3 innings, walking one and fanning six, but it wasn't enough to keep the A's (55-73) from falling to 2-11 in their last 13 road games.

"Other than that ball Gyorko hit out, I thought he pitched well against a team that hits well," A's manager Bob Melvin said of Detwiler.

Seung Hwan Oh nailed down the result with his 13th save, pitching around Alonso's leadoff single in the ninth by inducing a 6-4-3 double play from Ryon Healy. St. Louis (68-59) maintained its 1 1/2-game lead over Miami for the National League's second wild card spot.

Minutes after Oh retired Marcus Semien for the final out, Weaver's teammates dumped the contents of a water cooler on him.

"It was arctic," Weaver said, "and it was a lot of fun."

NOTES: St. Louis recalled RHP Miguel Socolovich from Triple-A Memphis Friday and optioned RHP Sam Tuivailala to the Redbirds. Socolovich is making his second appearance with the Cardinals this year. ... Oakland SS Marcus Semien was reinstated from the paternity list Friday and went into the lineup, batting seventh. Semien played in the A's first 124 games before missing the Cleveland series for the birth of his first child. ... Cardinals C Brayan Pena (left knee) caught four innings for the Rookie League GCL Cardinals, the first innings he's caught since starting a rehab assignment last week.