It seemed so easy under the Florida sun. Greg Bird was back in swing after his year off, tearing up the Grapefruit League.

Then the lights came on for the regular season. Now it seems so hard.

Bird claimed the Yankees’ everyday job at first base with a .451 run during spring training, but now that the season has begun, he has tripped over the starting blocks.

After going 0-for-3 with two strikeouts and a walk in the Yankees’ 3-2 win over St. Louis on Saturday at Yankee Stadium, Bird has seen his average plummet to .038.

That breaks down to 1-for-26 in his first seven games. Half of the 24-year-old lefthanded hitter’s outs have come on strikeouts.

Yet his confidence doesn’t sound shaken.

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“I can hit,” Bird said. “I know I can hit. I’ve just got to keep going, keep working and work through it.”

Joe Girardi said that’s still the plan, to let Bird swing away until he’s back in rhythm.

“I think he has to try to fight his way through this,” the manager said. “That’s what we’re doing. He walked his second-to-last at-bat, hit a ball hard the next at-bat. So maybe that’s the start of something good.”

The start of something good came on Aug. 13, 2015, when Bird arrived from Triple-A Scranton/Wilkes-Barre. He soon replaced an injured Mark Teixeira. During the remainder of the season, the 6-4 newcomer batted .261, led the Yankees with 11 homers and tied for the team high in RBIs with 31.

But he had injured his right shoulder in May of that year and finally underwent surgery to repair a torn labrum in February 2016.

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This year began better. Bird delivered 23 hits in 23 exhibition games, including seven doubles, a triple and eight homers. He also had 15 RBIs.

Yet there was no carryover.

“These things go in waves, I guess,” Bird said. “Obviously, you want to stay on the upside. But it’s part of the game. I’ve just got to keep at it and keep my head up and keep trying to be a part of the team.”

Bird fouled a ball off his right ankle/foot during an exhibition game against Philadelphia on March 30, causing a bruise. Swelling in the ankle as well as a stomach bug led to his missing four straight games April 8-12.

Asked if the injury has affected him at the plate, Bird said, “No, I’m going out there and giving everything I’ve got.”

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Chase Headley certainly can feel for him. The third baseman was the one who tripped over the starting blocks last season before eventually finding his way.

“You never want to see a guy get off to a tough start, especially with the spring training that he had,” Headley said. “He got a little banged up and the timing gets off. But I don’t worry about him. I mean, he’s going to hit. We’ve just got to keep running him out there, keep getting him at-bats. He’s going to figure it out.”

Girardi dropped Bird from third to sixth Thursday night in his first game back and then to seventh the last two games. He also gave Bird a vote of confidence Saturday morning.

Then a 99-mph fastball from Carlos Martinez whizzed by at the knees for strike three with two outs and the bases loaded in the first inning, followed by a swinging strikeout with runners on second and third and one out in the third.

“We believe in Greg Bird, and I believe he’ll get going,” Girardi said.

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He also said he knows Bird is frustrated.

“You want to do well,” Bird said. “But I’ll get it.”