"[We could be] 3-0," Mathieu said. "Every game this year we've started slow and ... we've lost three games by 15 points. It's not like guys are just blowing us out. We're really beating ourselves."
In their first three games, the Texans have scored 19 points and had 482 total net yards in the first half. That has jumped to 40 points and 707 total net yards in the second half.
"If I was a psychic ... I could tell you," receiver DeAndre Hopkins said. "I just do my job."
Added Mathieu: "I can't pinpoint it for you."
On Sunday, even the defense struggled in the first half, allowing the Giants to come away with points on each of their four first-half drives. On the other side of the ball, the offense managed just two field goals and was 1-of-5 on third down.
Because the Texans couldn't get the running game going in the first half -- an area that had been a highlight in the team's first two games -- Houston had to "basically [abandon]" it and rely on the passing game. Deshaun Watson threw 25 passes in the second half compared to 15 in the first half, and finished 24-of-40 for 385 yards with two touchdowns and an interception.
Regardless of the reason why the Texans have not been able to get off to a quick start, Mathieu said, "we just have have to play better."
"We play in phases where we dominate in one period, and the next period we look like we don't know what we're doing," he said. "The leadership, we have to be better. We've got to show up with intensity, with passion and just hold everybody accountable."
That starts next Sunday, when the Texans travel to Indianapolis to face the 1-2 Colts. At 0-3, Houston knows it doesn't have a choice but to come out swinging to start that game.
"We need to start fast, and we need to finish stronger," defensive lineman J.J. Watt said. "We figure it out for a little while in the middle, and we need to come up with a solution as to why and how we can get it going early and finish stronger at the end."