Denver Broncos coach Nathaniel Hackett says he "definitely" made a mistake opting not to run a fourth-and-five play instead of going for a 64-yard field goal in the closing stages of Monday's defeat to the Seattle Seahawks.

Hackett decided to send on kicker Brandon McManus with 20 seconds left to play instead of allowing quarterback Russell Wilson – playing against his former team – to run a play.

McManus could only drag his long-range effort left and thus allowed the Seahawks to take the knee for a 17-16 opening-round victory.

Since 1960 there have been only two kickers who have converted field-goal attempts of at least 64 yards, while the longest made at Lumen Field stands at 56. McManus is just one-of-five from 60-plus efforts.

Speaking to reporters on Tuesday, rookie NFL head coach Hackett conceded he got the decision wrong.

"Looking back at it, we definitely should've gone for it," Hackett said. 

"One of those things, you look back at it and you say, 'of course we should go for it, we missed the field goal'.

"But, in that situation, we had a plan. We had a plan, we knew the [46-yard line] was the mark."

Hackett explained how the plan to was to get into the 46-yard range, a target McManus said he was comfortable kicking from, and that he had more of an issue with a play earlier in the drive that saw Javonte Williams lose four yards on first-and-10 from Denver's 49.

"I'm more upset about that play before it, to lose yards," Hackett said. "Getting that there would've definitely been better to be able to call that same play and get extra yards. 

"[Wilson] dumps it out to Javonte, Javonte makes a move, goes a lot farther than I think we had anticipated. We were expecting to go for it on fourth down. 

"And then you hit the mark. The mark that we had all set before we started. We said, 46-yard line was where we wanted to be. And we got there, so we had to make the decision if we wanted to give it to Brandon. And we did. It didn't work. Sucks. But hey, that's part of it.

"Looking back at it, if you miss the field goal, you're always gonna wish you would've gone for it and if you would've gone for it and not gotten it, you wish you would've given him a chance."