There’s nothing more Dak Prescott can do to prove he deserves to start at quarterback for the Dallas Cowboys. He has exceeded every expectation and aced every test. He has won five out of six games, with the loss coming in his debut by a single point. On Sunday, he outplayed and beat Aaron Rodgers at Lambeau Field. He’s not as good as the Cowboys could have hoped. He’s better.

The Cowboys will face a decision when Tony Romo returns from his back injury, which should happen soon, perhaps as early as Week 8 following Dallas’s bye. Owner Jerry Jones said this week the situation requires “a tolerance for ambiguity” and that “there’s nothing simple” about it. But what’s plain, after the Cowboys’ 30-16 victory over the Green Bay Packers, is that Prescott is more than just a viable NFL quarterback and maybe even among the league’s best.

Under Prescott, the Cowboys have won five consecutive games, the past three without top receiver Dez Bryant. Sunday brought Prescott’s best performance yet. He completed 18 of 27 passes for 247 yards and three touchdowns. He threw 176 passes to start his career before Packers safety Morgan Burnett picked him off late in the third quarter Sunday, which set a new NFL record.

The performance may have eliminated the ambiguity in Jones’s mind. All along, Jones vowed Romo would not lose his starting job — which he has held since 2006 — when he returned from injury. He wanted to avoid a controversy. Prescott may have avoided the controversy in a stunning manner: He has played so well, and the Cowboys have coalesced around him with such confidence, Jones and the Cowboys may have no choice but to stay with him.

It would be difficult to spurn Romo. In his last healthy season, Romo led the Cowboys to within one controversial incompletion to Bryant of the NFC title game. Unless his back injury has diminished his ability significantly, Romo is still one of the best passers in the NFL. But it would also be difficult for the Cowboys to trust Romo, who played only four games last season, to stay healthy, or to bench Prescott and ask its offense to break the rhythm and momentum it so clearly has.

“Watching Prescott against Cincinnati, it’s his football team,” former Cowboys coach Jimmy Johnson said on “Fox NFL Sunday.” “Romo should be the best, most talented, most expensive back-up in the league.”

And Prescott’s success cannot be cast aside as a fluke. The Packers, one of the NFL’s toughest defenses, had five games of film to study Prescott, to prod for weaknesses, to figure out a strategy he could not solve. It didn’t matter. Some recent rookie quarterbacks, to thrive immediately, like Robert Griffin III or Colin Kaepernick, relied on their running ability and suffered physical consequences. Prescott provides a running threat, but he plays from the pocket.

In his first five games, Prescott displayed either an inability or unwillingness to throw deep. On Sunday, he showed he can do it when necessary. With one minute left in the second quarter, the Cowboys took over on their own 3. After three runs pushed them to the 38, Prescott dropped a pass down the right sideline to Terrance Williams for 42 yards. On the next play, he tossed another deep spiral to Brice Butler for a 20-yard touchdown and a 17-6 lead.

Prescott continued to show savvy and poise beyond his experience. Clinging to a 20-9 lead early in the fourth quarter, the Cowboys faced third and one in their own territory. Prescott made a canny play-action fake to Ezekiel Elliot, calmly dropped back and floated a pass to wide-open Lucky Whitehead for 35 yards. Prescott finished off that drive with a bootleg to his right to find wide-open Cole Beasley, his third touchdown pass of the game giving the Cowboys a 27-9 lead.

Prescott’s performance put him in rare company. Rodgers had been 52-13 in his career at Lambeau, and he walked off a loser for the 14th time. The Cowboys exited the ancient stadium with their fifth straight win and facing a bye week. It’s still not certain who will play quarterback the next time the Cowboys take the field. Prescott had just made an awfully convincing argument.