For weeks, Aaron Boone considered Paul Blackburn a secret.

Despite the right-handed reliever piling up zeroes out of the bullpen, he was going unnoticed.

That’s beginning to change.

“About a week ago, 10 days ago, somebody asked me about the job he had done,” Boone said after Blackburn delivered two innings of shutout relief to help the Yankees take Game 2 of Wednesday’s doubleheader over the Pirates, 2-0, and salvage a split in The Bronx. “It had been about a month-plus of some really good work — whether it be a high-leverage situation, whether it’s giving you multiple innings on a given night.

“It’s been about six weeks where he’s gotten his stuff in a really good place. He’s another guy like [Brent] Headrick, you feel good about going through lefties and righties. He’s been big for us.”

Yankees pitcher Paul Blackburn (58) reacts to getting out of the seventh inning with men on when the Yankees played the Pirates in Game 2 of a doubleheader on Wednesday. Robert Sabo for NY Post

The veteran righty is enjoying a terrific year, pitching to a 2.00 ERA after his latest performance. He has given up just one earned run over his past 14 appearances dating back to June 21 spanning 21 ¹/₃ innings.

After using high-leverage arms David Bednar, Fernando Cruz and Headrick in the opener, Blackburn’s two frames were integral to the victory. He inherited a runner on first base in the seventh, and when Jared Triolo stole second and went to third on catcher Ali Sánchez’s throwing error, the Pirates were set up to take the lead.

But Blackburn struck out Ryan O’Hearn and Marcell Ozuna to escape trouble, and the Yankees broke through in the bottom half of the inning.

The 32-year-old veteran joined the Yankees last year after he was released by the Mets in August. He didn’t perform well, but he enjoyed his time in The Bronx and returned on a one-year deal. This year, he has taken off.

“Just when I showed up last year, I didn’t know what to expect,” Blackburn said. “I walked in, there was a plan for me from day one. It just seemed like they were interested in helping me and getting me back to where they thought I could be.”

One major factor: increased velocity. It is up across the board for Blackburn. He is averaging a career-best 94.2 mph on his sinker, up from 92.6 a year ago, and it has made his secondary pitches more effective.

“I had a full offseason this year,” Blackburn said. “I focused on little different things I needed to get stronger and [gain] more mobility. Just ran with it.”