EAST RUTHERFORD, N.J. — When Daniel Jones was in high school, his mother, Becca, would ask him what he was going to do that day.

“Get better,” he would tell her every time she’d ask.

It became a running joke in the family, but Jones likes speaking things into existence.

At minicamp in the N.F.L. after his college career at Duke, he started grasping the Giants’ offense so quickly that his fellow rookies wondered whether he had received the playbook before they did. He had not.

But on Sunday, in his third start since replacing Eli Manning as the starting quarterback, Jones absorbed his first defeat, 28-10. When the Minnesota Vikings (3-2) weren’t cleaving the Giants’ facade of defensive proficiency on Sunday, they were tormenting Jones in ways, and to degrees, that he had not yet encountered.