TAMPA, Fla. — The rule is supposed to be 24 hours. That’s how long NFL players are expected to brood over a loss before they clear their heads, reset their emotions, and move on to the next game.

Jonathan Casillas has been in the league for nine years and seen all the ups and downs that a player can. He knows that 24-hour rule. And as he stood at his locker after Sunday’s 25-23 loss to the Bucs, he knew that it would be broken.

“It might be a little bit longer than that,” Casillas said. “No one ever predicted for us to do anything like that. It’s going to be really hard to swallow this one. We feel like we had it in the bag.”

For the second week in a row, they did. And for the second week in a row, fourth-quarter failures in all three phases of the game plan — offense, defense and special teams — led to a collapse that kept the Giants from notching their first victory.

Another field goal as time expired, this time from Nick Folk from 34 yards away, saddled the Giants with an 0-4 record. The last time they started this poorly was in 2013, when they began with six straight losses.

That team had limitations that everyone could see. This one? Many people predicted they would be in the playoffs and maybe contend for another Super Bowl. The Giants themselves thought that. Which makes this game and this first month of the season all the more soul-crushing.

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“We’re two field goals away from being 2-2,” guard Justin Pugh said of the back-to-back walk-off losses. “Obviously, you can’t look at it like that. But it’s so hard to win in the NFL, and we keep finding that week in and week out.

“We feel like [expletive],” Casillas said. “Everybody does.”

From the bottom, all the way to the top.

“We need to win a damn game,” head coach Ben McAdoo said.

They very nearly did. Eli Manning hit tight end Rhett Ellison on a play-action pass out of a funky formation that included defensive end Kerry Wynn at fullback for a 2-yard touchdown with 3:16 remaining to give the Giants a 23-22 lead. They attempted a two-point conversion pass to Odell Beckham Jr. in the back of the end zone, but he had run out of bounds before catching the ball, which negated the play and left the lead at a perilous one point.

“I was hoping that it wouldn’t come back to bite us,” Pugh said of the missed opportunity. “But after [Folk] missing those two field goals [earlier in the game], I was feeling pretty confident.”

Instead, the Bucs drove to the 13 and Folk came out to win the game as time expired.

“You’re just hoping you have another opportunity or the defense makes an interception or a tip ball, sack-fumble, something,” Eli Manning said of helplessly watching the lead wither away. “Stop them on fourth down.”

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They could not.

“It’s very tough,” Collins said. “That’s when the defense needs to step up and make a play. We lose by a field goal. It’s tough. You fight your butt off to hold them and they just march it down the field to get into field-goal range.”

Before the Ellison touchdown that gave the Giants the late lead, the Buccaneers took a 22-17 lead with 7:44 left when Jameis Winston hit Cameron Brate on a 14-yard touchdown pass. The drive was set up by a 15-yard punt by Brad Wing that went out of bounds at the 43. Linebacker Jonathan Casillas slipped in coverage. The Bucs went for a two-point conversion but Winston’s pass for DeSean Jackson was broken up by Eli Apple.

Folk kept the Giants in the game. He missed a pair of field goals and an extra point — seven total points — through the first three quarters that left the Bucs within arm’s length of the struggling Giants. His third missed kick, a 49-yard field-goal attempt with 10:10 left in the third quarter, gave the Giants the ball at their own 39 while trailing 16-10. They then embarked on a 61-yard, 11-play drive for a go-ahead touchdown.

Brandon Marshall pulled in a pass from a scrambling Eli Manning for 10 yards on third-and-5 from the 14, and two plays later, running back Wayne Gallman caught a 4-yard pass for a touchdown in his first NFL game. That made it 17-16 with 4:19 left in the third.

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The Giants had a chance to extend their lead early in the fourth but Aldrick Rosas missed the first kick of his career, a 43-yarder that went wide right. On the ensuing possession, the Bucs drove to the Giants’ 35 and attempted a fourth-and-2 conversion. Landon Collins broke up a pass intended for Brate that gave the ball back to the Giants. It was a play similar to the one Brate would make on the final drive to set up the winning field goal.

“Last year, those games didn’t happen to us,” Pugh said. “We won those games last year.”

This year they are not. Habitually.