MILWAUKEE — From college walk-on to major league starter, Chicago Cubs right-hander Alec Mills had to earn most every break he got.

On the brink of big league history, he was happy to welcome this bit of luck: expecting to see two-time batting champion Christian Yelich in the on-deck circle, Mills looked over and saw his backup instead.

“That kind of surprised me,” he said.

This one surprised just about everyone.

Mills cruised through baseball’s second no-hitter this season in just the 15th start of his career, completing the gem in a 12-0 romp over the Milwaukee Brewers on Sunday.

Mills got Jace Peterson — who replaced Yelich, the 2018 NL MVP, on defense late in the blowout — to hit a routine grounder to shortstop Javier Baez with two outs in the ninth. Baez completed the play, and the Cubs swarmed around Mills, tearing off his cap and pulling at the smiling right-hander’s uniform after his first career complete game.

“It just hasn’t really hit me yet,” the 28-year-old said. “It’s kind of crazy, I didn’t even know how to celebrate. Just something that all came together today. Obviously a memory I’ll have forever.”

Mills (5-3) threw 114 pitches and hardly had any close calls in Chicago’s 16th no-hitter. Avisail Garcia almost got to him twice, hitting a line drive to right in the first and nearly legging out an infield hit to shortstop in the sixth. Garcia crossed first and immediately called to the Brewers dugout for a review, but after a very brief stoppage, the Brewers opted not to challenge.

Mills would have faced Garcia again in the ninth, but Milwaukee manager Craig Counsell pulled the 2017 All-Star along with Yelich in the eighth with his team trailing big. Mills struck out Garcia’s replacement, Tyrone Taylor, for the second out in the ninth.

“Taylor hitting there and then Peterson, I had no idea they were in the game,” Mills said.

Mills struck out five and walked three. His five strikeouts are the fewest in a Cubs no-hitter since Ken Holtzman in 1969.