CHARLOTTE -- Every week in the NFL is a referendum on the quarterback.

In 2016, Dak Prescott played as well as any rookie quarterback in NFL history, leading the Dallas Cowboys to a 13-3 record with 23 touchdown passes and four interceptions, which was good enough for him to be the Rookie of the Year.

In the first eight games of the 2017 season, Prescott showed the ability to carry the Cowboys to wins with his arm, legs and guile. He had 16 touchdown passes and four interceptions as the Cowboys got off to a 5-3 start.

Since then, things have changed, and not even the return of Ezekiel Elliott from a six-game suspension seems to be a fix.

Sunday's season-opening loss to the Carolina Panthers looked quite similar to how the Cowboys ended the 2017 season.

Prescott completed 19 of 29 passes but for only 170 yards. Dating back to last season, Prescott has throw for less than 200 yards in seven of his past nine games. He did not throw a touchdown pass for the sixth time in his past nine games. He was not intercepted, but he lost a fumble on the Cowboys' final drive following the sixth time he was sacked.

The only other time Prescott has been sacked more came in the unforgettable loss at the Atlanta Falcons in which he was dropped eight times, six by Adrian Clayborn.

"I was off," Prescott said. "That stuff you have to go back and look on film. I have to figure out what I was off. Was I rushing it? Did I feel pressure? What were the things causing it? Was it just me missing the pass? That's not anything that I can judge right now."

Entering Sunday's game, Prescott acknowledged the importance of the upcoming season for him personally, with the Cowboys having the ability to sign him to a huge-dollar, long-term deal after the year.

"If I play my game, I do what I am asked to do, all that stuff will come. It's not anything I worry about," Prescott said.

After his rookie season, Prescott seemed like he was well on his way to being a more-than-suitable replacement for Tony Romo and maybe a Super Bowl winner, like Hall of Famers Roger Staubach and Troy Aikman. That progress seemed to continue through the first eight games of last season.

Part of Sunday's ineffectiveness can be pinned on mistakes by others that saw Prescott facing third-and-26, third-and-17, third-and-10 and third-and-11 on the first four possessions.

"As much as anything else we had some minus plays," coach Jason Garrett said. "We had some sacks. We had some negative plays. Just because you're not throwing the ball down the field doesn't mean you don't have [deep passes] called. Sometimes the ball has to come out quicker because you have some pressure. You have to do something, so we tried to stay aggressive and tried to attack ... Their style is to play it out a little bit and make you earn it."

When Prescott had a chance for a big play on third-and-7 on the Cowboys' fifth possession, he missed a wide-open Blake Jarwin.

"I think I initially pulled the ball down, was thinking, 'Run for it,' looked up and saw him," Prescott said. "Just have to make that throw."

Prescott did not blame the lack of preseason action for his struggles. He did not play in the final two preseason games after playing in 39 snaps in the first two preseason games. He did not put anything on the absence of Pro Bowl center Travis Frederick, who will miss an undetermined amount of time with Guillain-Barre syndrome. He did not blame the absences of his top two pass-catchers from a year ago, Dez Bryant and Jason Witten.

"I know we have a lot of great players on this team. A lot of good guys that come in and work the right way every day and gave everything they had tonight," Prescott said. "I'm not talking about the guys we used to have or guys that we're missing. I felt like the guys on the field tonight, we gave it our all and [I] promise we'll do it again next Sunday and have a better performance."

When Prescott hit something of a slump in his rookie year -- back-to-back games with less than 200 yards passing -- he responded by completing 89 percent of his passes the following week. After a 42-17 Week 2 loss last year at the Denver Broncos in which he was intercepted twice, Prescott threw 13 touchdown passes to just two picks in the next six games.

But something has changed since. Prescott and the coaches have to come up with answers, or else the questions will continue to grow.