Chase Headley has heard it all. He’s done. Washed up. Can’t play anymore.

He doesn’t believe it.

“I’m a good player,” Headley said before Thursday night’s game. “I know I’m a good player. And I haven’t been a good player this year. That’s frustrating to me. The notion that I’m not good enough, that’s not true. That I don’t think it’s coming back or I can’t be that player, that’s not there. I know that I’m going to, eventually. Sooner rather than later. It’s not easy going through it. But as far as, ‘I’m just going to try to hang on or do the best I can to survive,’ I don’t have that.”

The Yankees third baseman made his calm but impassioned defense of his abilities before hitting his first home run and (first extra-base hit) of the season, a two-run shot to left, in the Yankees’ 7-3 victory over the Royals at Yankee Stadium.

As he spoke, Headley’s voice didn’t rise and there was no dramatic music in the background. But his message was clear: Headley believes he’s going to be good again.

Thursday night was a start.

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“Zero doubt,” Headley said. “Zero doubt. I’m confident that at the end of the year my numbers are going to look the way that they always do.”

They looked awful heading into Thursday night. Headley was batting .178, which was also his slugging percentage because all 16 of his hits had been singles. His slugging percentage was the lowest of any regular player in baseball, by far. Now the average is .194 and the percentage is .226 after Headley went 2-for-3 with a walk.

“It’s been pretty crummy for a while,” Headley said. (Potty mouth.)

Headley’s second-inning home run off former Yankee Ian Kennedy didn’t travel far, but it went far enough to the opposite field, and it started an avalanche of celebrating in the Yankees dugout. The second hit was a line drive to left batting right-handed in the eighth.

Headley has seven hits in his last 18 at-bats, a four-game hitting streak and at least one RBI in each of his last three games after going a career-long 23 games without driving in a run.

“Just really good to see,” manager Joe Girardi said. “Chase is loved in that clubhouse.”

Maybe so, but he’s not getting any bouquets from Yankees fans. For a long time, Headley looked more like a candidate to be released than a candidate for a comeback. But the Yankees have no other options at third and Headley, 32, is in the second year of a four-year, $52-million contract.

It’s not a Jacoby Ellsbury-bad contract. But it’s not a bargain.

Headley, who insists his troublesome back is not an issue, recently asked to see the Yankees’ internal advanced statistics to find out what the numbers behind the numbers showed.

“It’s a healthy dose of reality,” he said. “Just to be honest with yourself I think is important. Honestly, there were some really encouraging things in it, like my swing and miss [rate], my chase percentage, my exit velocity — they were all in line or better than where they normally are.”

Headley admitted his line-drive percentage was lower than it should be, especially batting left-handed. And, he said, “If I never hit another ground ball, I would be thrilled.”

The Yankees are paying Headley handsomely to hit doubles and homers to go along with the singles. Maybe not as many as in 2012, when he hit 31 home runs and had an NL-leading 115 RBIs for San Diego in what was by far his best season. But more than one.

Headley insists he can.

“I finally have my swing doing the things I want it to,” he said. “I know if I throw that swing out there, then it’s going to work.”