SAN FRANCISCO — Sergio Romo retired as a San Francisco Giant just the way he wanted to, pitching one final time for the team he helped to win three World Series championships, and then calling it a career Monday night.

In a moment more special than he could have imagined, the entertaining right-hander faced three Oakland batters in the seventh inning at Oracle Park in the exhibition finale for both clubs.

“Very fitting to find some closure in what literally is for me, was a storybook career,” he told reporters, pausing to catch his breath after the Athletics’ 12-6 win.

The Giants reached out a few weeks back to see whether Romo might consider tossing an inning — he looked at his arm and asked if it could give it one last hurrah. He had already taken up golf.

“I understand how special this opportunity was,” he said.

So, Bay Area baseball fans were treated to a last listen of Romo’s longtime signature “El Mechon” walk-up tune, too, and he basked in the cheers.

But ahead of unleashing his nasty slider, Romo got a dose of what he’ll be missing in the new, modern baseball world — he was immediately called for two clock violations by the plate umpire, resulting in a pair of automatic balls.

The first was for taking too long to finish his warmup tosses. The second was for taking too long to throw his first pitch.

Going against one of his former teams, and starting with a 2-0 count, Romo quickly walked his first batter. He threw a wild pitch and surrendered two singles that scored a run before former teammate Hunter Pence walked out to make a pitching change.

Romo, 40, soaked it all in as he made his way to the dugout, tipped his cap and hugged Giants manager Gabe Kapler and others in a sensational sendoff.

Romo got a curtain call and fought tears as he went back into the dugout.

Saluted with a rousing ovation when he strolled to the bullpen to begin his warmup tosses, Romo received more cheers when he came into the spring training game. The A’s players watched and clapped from their dugout rail, and the Giants grinned, witnessing the emotional goodbye to baseball.

Ever popular with the home fans, Romo wore a special hat. All during spring training, every time a kid asked for an autograph, he’d have them sign his cap.

“If this was the last hat I was going to wear in the big leagues … I figured it would be nice to not go in there alone,” he said.

Romo played 15 seasons for eight organizations, including the Athletics, spending his initial nine years with the Giants. The reliever on Monday shared a goodbye note to San Francisco on The Players’ Tribune.

“Dear San Francisco, Tonight I get to do something one last time – something that’s been one of the biggest honors of my whole life: I get to put on a Giants jersey. And before I go do that, I just wanted to write this letter, and share some thoughts with you all. Thanks for reading,” he said.

On Sunday in Oakland, Romo greeted fans and fist-bumped youngsters as he made his farewell rounds. On his Instagram account, the ever-creative Romo posted a photo of himself holding a sign similar to those of students on the first day of school but signifying his last day in the majors.

Romo grew up in Brawley, California, about 125 miles east of San Diego and some 30 miles north of Mexicali, Baja California, Mexico. He was a 2013 All-Star for the Giants and posted a career record of 42-36 with a 3.21 ERA and 137 saves over 821 appearances spanning 722⅔ innings. Last year, he pitched a combined 23 games for Seattle and Toronto.

He also played for the Dodgers, Tampa Bay, Miami and Minnesota. A 28th-round draft pick by San Francisco in 2005 out of Colorado Mesa University in Grand Junction, Colorado, Romo was a key member of manager Bruce Bochy’s stellar bullpen soon after making his big league debut in 2008.

Romo helped the Giants win every-other-year titles in 2010, ’12 and ’14 — the 2010 team capturing the franchise’s first championship since 1954 and first since moving West from New York in 1958.

Romo excelled in those games, posting a 0.00 ERA and three saves in six World Series appearances.

And long after those October highlights, Romo wound up on the very same mound for the last time, finishing up on a March night.

“What an experience,” he said.