There was a time when John Ursua might have gotten nervous.

Like maybe in grade school or something.

But quite a while ago, Ursua said he figured out that being on the field when the game was on the line was sort of the point of it all.

“In the big situations, I’m happy I get to go in,” Ursua said.

So even though he had barely played in his NFL career — just four snaps before Sunday — and had never caught a pass, when Ursua heard his name called before a critical fourth down in the final seconds against the 49ers, he felt only excitement.

“I was just smiling,” said Ursua, a rookie seventh-round pick out of Hawaii last April. “Coach Nate (Carroll, receivers coach) was like ‘JU, you are going in.’ And I was like ‘OK, let’s go.’ This is the biggest play of the game, and I was like, ‘Sure.’ It was absolutely a dream come true.”

Only one thing would have made it better — if Ursua had been in the end zone when he caught Russell Wilson’s pass on fourth-and-10 from the 49ers 12 that snapped with 42 seconds remaining.

Ursua, instead, caught the ball at the 1. Still, had Seattle not gotten a delay penalty (or a pass interference been called a few plays later, or Jacob Hollister been in the end zone on the next fourth down) then Ursua might have been one of the more unlikely heroes of one of the bigger regular-season wins in Seattle history.

So, as Ursua said, even if it was “cool and a great memory for me,” his first significant NFL experience was ultimately a little bittersweet.

He’s using it as a learning experience to turn it into one that is unconditionally sweet next time, as those who have gotten to know him since he became a Seahawk would expect.

Ursua was active for just the third time this season with Malik Turner out with a concussion.

When Jaron Brown suffered a knee injury on the first drive, Ursua moved up to be the fourth receiver behind Tyler Lockett, DK Metcalf and David Moore. He could stay in that role this week for the wild-card playoff game at Philadelphia depending on Turner’s situation, but with Brown likely out, Ursua figures to again be active.

The Seahawks, though, didn’t use a lot of four-receiver sets last Sunday and mostly left Ursua to watch from the sideline. Ursua said he spent much of the game doing anything he could to stay warm — riding an exercise back or standing close to the heater.

“But I had to stay close (to the coaches) in case my name was called so I could get in there,” he said.

That happened when Seattle reached the 12, and when, before fourth down, the Seahawks, and then the 49ers, called time out.

“They said we are going 0-1, which is no backs, all receivers,” Ursua said. “I was like, ‘Man, that’s me!’ “

Lockett and Metcalf were flanked to the left of Wilson, leaving Ursua in the slot matched up with San Francisco’s K’Waun Williams.

Ursua said he looked to the left at Lockett and Metcalf and figured Wilson would throw to that side.

But when he saw Williams press him at the line, he also thought Wilson “might come this way and come to me because this is great opportunity to get open with this press.”

It’s exactly what Ursua was used to doing in his three years at Hawaii, where, as a senior a year ago, he led the nation in receiving touchdowns with 16.

And Wilson, as he said this week, had “no hesitation” in thinking of throwing Ursua’s way should he come open.

Ursua was one of the receivers who attended Wilson’s informal offseason workouts in the Los Angeles area, the two ending up on a basketball team that Wilson said went 14-0 before finally losing.

Ursua also hits the field the same time as Wilson for pregame workouts.

He does so in part because Wilson urged him to since the preseason. As a rookie backup, Ursua spends much of his practice time with the scout team offense, meaning many of his passes come from Geno Smith.

Ursua said Wilson told him one day: “‘Hey, do you want to get 30-40 catches in with me, ‘cause we don’t get a lot of reps (in practice)? Come early when I throw early and we can knock that out and get a little chemistry going.”’

Wilson calls Ursua “relentless” in his preparation.

So as the play unfolded and Wilson moved to his right, he spotted Ursua and had no hesitation to make the throw in the biggest moment of the game.

“I was crawling outside the pocket, and there he is,” Wilson said. “And just let it rip.”

The play, Ursua said, called for him to go 4 yards deep in the end zone, then work his way back a little bit, if needed.

But, in what has been the big learning lesson of this week, the play called for him to make sure he stayed in the end zone.

“With a little bit of the break in the pocket and me trying to make sure that nobody could make a deflection on the ball, I kind of worked myself back out a little bit,” Ursua said. “So when I caught it I kind of went with the momentum rather than setting my feet and trying to spin out of it and score. Because I felt like if I had done that, I still could have scored. But I kind of lost surroundings a little bit where I was like, ‘OK, I think my feet are still in.’ “

As the play ended, Ursua still thought he was in the end zone and that he’d scored, until the officials spotted the ball just short.

The hard-to-fathom sequence that followed robbed Ursua of being a hero.

But a larger point was made about what the team can expect out of Ursua.

“It’s just a matter of time,” coach Pete Carroll said. “I think he could be a terrific receiver for us. … This is really good for him to be around where there’s a greater sense of urgency where he’s dressing and being a part. It’s going to bring out the best in John.”