He can be Good Big Mike one game and Bad Big Mike the next. Or even in the same game. Or inning. Or at-bat.

After a Bad Big Mike first start at Tampa Bay, Michael Pineda was Brilliant Big Mike for the Yankees in their home opener last Monday against the Rays. The 6-7 righthander brought perfection into the seventh inning, allowed one run, two hits and no walks and fanned 11 in 7 2⁄3 innings.

“It was tremendous,” Joe Girardi said before Pineda went out to start Sunday night’s game against the Cardinals at Yankee Stadium. “We need him to build on that.”

Basically, he did. The Yankees won, 9-3, to finish off the three-game sweep and extend their winning streak to seven games, and Good Big Mike helped do it.

Yes, some of his bad habits showed through, but not enough to detract from a strong outing. Pineda allowed two runs, six hits and a walk and fanned six in seven innings. Sixty-six of his 96 pitches went for strikes.

“I didn’t think his slider was as sharp as the other day,” Girardi said, “but he found a way to get through seven innings.”

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Greg Bird broke out of his season-opening slump with a single, double, two-run homer and walk in his first career three-hit game.

The Yankees (8-4) are 6-0 at home for the first time since their 1998 championship season. “It’s another win for us,” Bird said. “If I can contribute, that’s huge.”

Pineda moved to 2-1 with a 3.44 ERA after finishing last season 6-12 with a 4.82 ERA in 32 starts. He struck out a career-best 207 batters and served up a career-worst 27 homers in 2016. Opponents hit .303 in the first two innings and .325 overall with two outs.

“I don’t really see Michael’s mind wandering,” Girardi said before the game. “This man is full of gyrations anyway. You wonder what’s going through his mind when he’s doing all that anyway. But I don’t really see it that he’s not focused . . . I think he wants to be focused and I think he wants to make a pitch, but sometimes he doesn’t.”

This time the 28-year-old free agent-to-be retired the first two batters of the game. He found two-out trouble thanks to a walk and a bunt single, but he escaped, striking out Matt Adams swinging.

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In the second, Pineda couldn’t escape his two-out problem. Greg Garcia drove in Jedd Gyorko from second, lining a single to left for a 1-0 lead.

Chase Headley led off the bottom of the inning with a single against Adam Wainwright and Aaron Judge followed with a drive toward the right-centerfield wall. A fan reached out with his glove and dropped the ball, which ultimately was ruled an RBI triple after video review.

Bird was next, standing in with no homers, 20 straight hitless at-bats and one hit in 26 at-bats overall.

“My timing was messed up,” he said.

“I just think he’s a little out of whack,” Girardi had said.

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Not this time. On the pitch after Judge’s triple, Bird whacked a souvenir to the fans in the right-centerfield bleachers, good for a 3-1 lead.

“Tonight I tried to simplify and swing at strikes,” Bird said.

Aaron Hicks made it 4-1 in the fifth, belting a homer just inside the rightfield foul pole off a disbelieving Wainwright, who allowed 10 hits in 4 2⁄3 innings.

Austin Romine and Ronald Torreyes had back-to-back two-run doubles with none out in the eighth to give the Yankees an 8-2 lead. Hicks added a sacrifice fly to cap the five-run inning.

Pineda, meanwhile, found his rhythm, retiring 15 of his final 17 batters. He showed off his dominant side in the fourth, getting Yadier Molina and Randal Grichuk swinging at 96-mph heat.

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“After the second, I got more energy,” he said.

There was a mistake in the seventh. Molina hit a hanging 0-and-2 breaking ball into the leftfield seats to open the inning. But Pineda retired the next three to finish his second straight quality start.

“For me, it’s important,” he said, “because I’m working so hard to be consistent every five days.”