OAKLAND — After activating Mason Miller off the injured list on Wednesday morning, the A’s wasted no time getting their All-Star closer back in action in Wednesday’s 3-2 win over the White Sox.

With the A’s taking the lead in a three-run seventh inning keyed by back-to-back RBI singles by Armando Alvarez and Zack Gelof and Lawrence Butler’s sacrifice fly, Miller was summoned in the ninth inning for his first appearance since fracturing the pinky on his non-pitching hand on a padded training table following a July 22 appearance.

The flamethrowing right-hander showed no signs of rust, finishing off Oakland’s series finale victory by retiring all three batters faced for a perfect inning to notch his 16th save of the year. Of Miller’s 13 pitches, nine registered at 100 mph or faster, with his blazing fastball maxing out at 102.2 mph.

“He picked back up where he left off,” said A’s manager Mark Kotsay. “You don’t know what you’re going to get from a first outing [back]. He didn’t go on a rehab assignment, so there’s those thoughts going through your head of how he’s going to come out and enter into competition. I think it was a great first outing for him.”

Miller threw eight of his 13 pitches for strikes as he retired Andrew Benintendi, Lenyn Sosa and Dominic Fletcher in order — all via flyout. He added to his ongoing Major League lead for most pitches of 100 mph or greater, bringing that total to 315.

“Not anything crazy,” Miller said when asked if he felt rust after not pitching in a game in over two weeks. “Obviously, you’re getting your sea legs back under you a little bit. But I felt good. That’s the only way you can [shake off rust] is to get back in there. … I’m just excited to be back and part of the group.”

The late-inning makeup of the A’s bullpen has changed a bit since the last time Miller had pitched. Back then, he and setup man Lucas Erceg had formed quite the formidable duo as high-velocity relievers. Erceg, of course, is now a member of the Royals after the A’s dealt him to Kansas City at the July 30 Trade Deadline in exchange for three prospects.

During Miller’s stint on the IL, the A’s identified another high-leverage option in Tyler Ferguson, who prior to debuting in May, spent eight seasons in the Minors along with some time in independent leagues such as the Canadian-American League and American Association.

Ferguson notched a pair of saves while Miller was sidelined and became a trusted option for Kotsay in late-game situations. With Miller now back, Ferguson has earned a chance to settle into that setup role once occupied by Erceg, which the 30-year-old right-hander performed flawlessly on Wednesday with two strikeouts in a perfect eighth to hold a one-run lead.

“We traded one of our leverage pitchers in Lucas Erceg,” Kotsay said. “With how Ferguson is throwing the ball and stepping up in those leverage roles, it’s an example of having someone come in that has built confidence in fulfilling that role.”

With Wednesday’s win, the A’s clinched their fifth series victory in their last seven tries. Their 18-12 record since the start of July is the best in the American League and third-best in the Majors over that span, keeping them on a good pace to achieve their team goal of finishing the season with a second-half record above .500.

Up next is a six-game road trip that begins on Friday in Toronto for three games and goes through New York for three more games against the Mets. That trek to the East Coast for the A’s will carry the boost of knowing they have their electrifying closer in Miller back and looking as dominant as usual.

“I love having him back,” Gelof said. “Whenever he’s on the mound, I have nothing but confidence. Sometimes I catch myself just watching him throw and I remember I have to get ready to field the ball if it comes to me. It’s just great to have him back. He’s a big part of this team.”