In real time, it appeared Cooper Kupp made a great effort to dive for a drive-extending first down late in the fourth quarter.

The Seahawks receiver was quickly ruled short of the line to gain, however, and replay upheld that decision, ending Seattle's comeback hopes with a turnover on downs. The 49ers were then able to run out the clock for a 32-29 victory.

"They said he was short, so we've got to live with it," Seahawks coach Mike Macdonald said after the loss.

Kupp, while disappointed he was unable to get the first down, did not object to the decision.

"I knew it was close, but clearly it was short," Kupp said. "There's not enough there, I've got to find a way to get that fourth down."

In an interview with PWFA pool reporter Brady Henderson from ESPN, vice president of instant replay Mark Butterworth explained the decision. Below is a transcript of the interview, which also includes an explanation on the decision to eject 49ers linebacker Dre Greenlaw for headbutting a helmet-less Ernest Jones IV on the sideline:

Question: Can you tell me what you saw on the replay of the Seahawks' final offensive play?

Butterworth: "Because it's the end of the game and really a game-deciding call on the field, we purposely stopped the game to look at the entirety of the play. With all of our available angles, including our boundary line cameras, there was no video evidence to overturn the call on the field. A key thing to remember is we are looking at when the ball breaks from green, the field of play, to white, out of bounds. There was nothing clear and obvious to overturn the call on the field."

Question: Can the ball continue to be advanced towards the line to gain when it is out of bounds?

Butterworth: "The runner was going from inbounds to out of bounds. So, when that next body part is out of bounds, we're looking at where the ball crosses the sideline."

Question: So, in other words, he could be in the air, having not touched out of bounds, and if the ball is practically on the other side of the out of bounds line, can it still be advanced over the line to gain?

Butterworth: "No. In your example, if the player is airborne, we are still looking at where the ball breaks from green to white – green meaning the field of play, white meaning out of bounds. It's not where his body part lands out of bounds, it's where the ball breaks the plane from inbounds to out of bounds."

Question: So once that happens, then the ball is out of bounds?

Butterworth: "Correct."

Question: So it's not like the goal line?

Butterworth: "The line to gain we treat differently than the goal line. The runner gets goal line extended with a body part in the end zone. For the line to gain, we are looking at where the ball breaks from green to white."

Question: Was that confirmed or upheld?

Butterworth: "We only have stands or overturned, so we stood with the ruling on the field."

Question: On Dre Greenlaw's ejection, what led to it and what was the process of ejecting him?

Butterworth: "The clubs passed a rule this year that the AMGC (Art McNally Gameday Central in New York) can actually eject a player even when there is not a flag down on the field for the action. But in this case, there was a flag down on the field. When they went to the sideline, the player in question actually head-butted a non-helmeted player on the sideline. We have a very specific process we go through. (NFL Executive Vice President of Football Operations) Troy Vincent let us know that the player was ejected, so then I communicated with the field to inform them that number 57 was ejected from the game for a non-football act."