Dak Prescott had a long day in Denver. (Jack Dempsey/Associated Press)

It took more than a year, but Dak Prescott finally learned how hard it can be to play in the NFL. During his charmed rookie season, his offensive line was impenetrable, his running back was untouchable and his poise was unflappable. Every NFL player, no matter how great, has a day when everything unravels. On Sunday, that day finally came for Prescott.

The Denver Broncos plastered the Dallas Cowboys, 42-17, a notable result because it showed the Broncos may actually have enough offense to contend in the AFC and because Prescott had never before been plastered as a professional. Prescott breezed through his rookie season without a day like Sunday, when nothing goes right. He was so good, and everything around him was so smooth, that he never really had to bounce back. It was a matter of time before he would, and the time came two weeks into this season.

Throw out the Cowboys’ regular season finale last season, when they sat their starters in the second half and conceded, and Prescott’s three NFL losses, including playoffs, had come by one, three and three points. In every game Prescott cared about winning except one, the Cowboys held a lead or were tied in the fourth quarter.

On Sunday, the Broncos crushed Prescott and the Cowboys from the start. Their pass rush cleaved Dallas’s typically flawless offensive line, sacking him twice but hounding him all day. Denver’s offense gashed the Cowboys, forcing the Dallas to desert its running game and rely on Prescott, who attempted a career-high 50 passes while Ezekiel Elliott rushed only nine times for eight yards.

Prescott had only trailed by double-digits once in his NFL career, when the Cowboys fell behind the Packers 21-3 in the divisional round last year. On Sunday, the Cowboys trailed by 25 points, which turned out to be the final margin, early in the fourth quarter.

Prescott had thrown multiple interceptions in a game only once, and in fact, Prescott became the first quarterback in NFL history to throw less than five interceptions in his first 500 pass attempts. But he still threw two picks, one of them through the hands of Dez Bryant, his best wide receiver.

The debacle, so stark in contrast to the rest of Prescott’s career, served to remind what a singular rookie season Prescott enjoyed. He usurped a veteran’s position, but his excellence combined with Tony Romo’s grace allowed Prescott, somehow, to take the reins with almost no controversy. He earned the job to such an extent everybody, including Romo, had to admit it.

His charisma, talent and leadership enabled him to take charge of the Cowboys as a fourth-round draft pick, but he also landed in an ideal position. He could hand the ball to Elliott, the fourth overall pick and instantly one of the NFL’s best running backs. He had the best offensive line in the league to protect him. He had a creative offensive coordinator in Scott Linehan and a longtime quarterback overseer in Jason Garrett.

Now, though, Prescott may grow accustomed to adversity. Prescott may have to direct the Dallas offense without Elliott, depending how the case regarding his six-game suspension and appeal winds its way through the court system this week. The Cowboys will play at Arizona, an opponent with a strong pass rush, on Monday night.

There’s no alarming takeaway from Prescott or the Cowboys’ performance in Denver, as bad as it was. There are going to be days like Sunday in the NFL, and Prescott had one. It was notable only because it had never happened before.

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