QB HERBERT UNKNOWN QUANTITY ON NFL LEVEL

The Chargers had 14 seasons of Philip Rivers’ on-field bravado, 235 consecutive starts by a quarterback who rarely saw a throwing window too small and eagerly accepted any risk for whatever reward.

After four starts, what do they have in Justin Herbert?

“I think it’s too early to decide that,” Herbert said. “Obviously, I’d love to complete every pass that I throw. But it’s not going to happen. I’m going to make mistakes.”

Rivers never shied from taking chances when he saw opportunity. He often shrugged off interceptions, particularly those thrown in desperation late in first halves or at the end of games.

That attitude, buttressed by his unending belief in his right arm, shaped Rivers into the quarterback that he was with the Chargers — a playmaker who also could make crushing mistakes.

The style clashed with the preferences of coach Anthony Lynn, who preaches, above all else, limiting turnovers. The Chargers, who are off today, have dropped their last nine games when losing the turnover battle.

“I think I should always be alert and prepared to take care of the football … make smart decisions,” Herbert said. “It should never feel easy or anything like that out there.”

Just before the two-minute warning in the second quarter Monday, Herbert was faced with weighing the risk against a potential reward he spied deep down the middle of the field.

On third-and-12 from the Chargers’ 16-yard line, he scrambled from pressure to the left sideline and, rather than step out of bounds, fired toward a well-covered Jalen Guyton.

The one thing the Chargers didn’t need at that point was a turnover to set up New Orleans with a short field.

A fumble near the end of the first half already cost them a gamechanging touchdown in Week 4 at Tampa Bay.

This time, Herbert threw long enough that the ball sailed over the head of Guyton and the two Saints defenders and fell to the turf just beyond midfield.

The Chargers then punted but gave up a 14-yard return, and New Orleans took over at its 49 anyway. Eight plays later, the Saints scored to cut a 17-point deficit to 10 entering halftime.

So Herbert avoided giving away the ball, but the Chargers still couldn’t avoid giving up another crucial last-second score.

“I gave him a chance to go make a play,” Herbert said. “Yeah, I could have made a better ball. But that’s a decision I stuck with. … Yeah, I could have been more cautious. But I really believe in that guy.”

Entering Week 6, Herbert was ninth in the NFL in passer rating at 107.1, just two-tenths of a point behind Patrick Mahomes.

Only Dak Prescott (sidelined for season), Aaron Rodgers and Derek Carr had more completions for 40 or more yards, confirmation that Herbert possesses the ability for the quick strike. He has an interception rate of 2.1 percent, which ranked 17th out of the 32 quarterbacks with enough attempts to qualify.

In four years at Oregon, Herbert hardly was reckless. He was picked off 23 times in 1,293 attempts (1.8 percent). He never had more than eight interceptions in a season or two in a game.

History suggests he’ll take care of the ball over attempting to squeeze passes into areas where overriding danger lurks.

But, ultimately, Herbert’s precision won’t just involve keeping the ball out of the hands of defenders. He’ll also need to fine-tune his game to meet what the NFL requires of quarterbacks trying to take over franchises — an exactness he lacked on the final two plays Monday.

Facing third-and-seven, Herbert missed an open K.J. Hill, throwing well behind the rookie wide receiver on a play that would have gained at least 12 yards.

Herbert then connected with Mike Williams, but his pass was right on Williams rather than slightly ahead of him.

Lynn said better ball placement would have secured a first down. Instead, Williams was stopped inches short.

“We did some great things and we did some not-so-great things,” Herbert said, speaking of the offense in general.

“It’s all about fixing those notso-great things.”

For the third time in his four games, Herbert won a rookie of the week honor Friday. So he’s 3-1 in personal recognition but 0-4 in the NFL standings.