Chargers quarterback Taylor Heinicke hands off the ball to running back Gus Edwards during the fourth quarter Sunday.

(Matt Freed / Associated Press)

This is why Taylor Heinicke is here.

The Chargers traded a conditional sixth-round pick to the Atlanta Falcons for the 10-year veteran knowing they needed to upgrade their backup quarterback in the event Herbert was injured. The moment no one was waiting for came Sunday.

With just 24 days of experience with the organization, Heinicke entered the game in the third quarter and completed both of his pass attempts for 24 yards, but was sacked three times behind an offensive line that lost starting left tackle Rashawn Slater to a pectoral injury.

“Wish we would have given him a little more time there to operate, but I was pleased with his performance,” head coach Jim Harbaugh said of Heinicke. “He’s a competitor. Competitors are welcome here at the Los Angeles Chargers.”

Incumbent backup Easton Stick had a head start on the scheme by playing in all three preseason games, but Heinicke caught up by burying his head in the playbook for three weeks. The system was so complicated that he struggled to even say a play out loud at first.

He was inactive for the first two games while still getting up to speed. Then Heinicke started taking the majority of practice reps by the end of last week when Herbert was limited in training, helping him comfortably lead the offense despite the mid-game injury.

Although Harbaugh immediately dismisses any “what if” questions, Heinicke has had to live in the hypothetical for a decade. The longtime backup has made a career out of preparing just in case and is prepared to do it again as Herbert monitors the high ankle sprain.

“We’ll see how this week goes,” Heinicke said.