LAS VEGAS >> It used to be one of the easiest decisions in football: If you win the toss in overtime, you take the ball.

The rules are different now, however, and that choice by San Francisco in the Super Bowl will be debated all offseason.

The 49ers took the ball and drove for a field goal, then lost 25-22 when Patrick Mahomes guided Kansas City 75 yards the other way for the winning touchdown tonight. San Francisco’s drive ended when the 49ers kicked a field goal on fourth-and-4 from the 9.

If they’d known three points wouldn’t be good enough, they could have gone for a touchdown in that spot.

“That’s something we talked about,” San Francisco coach Kyle Shanahan said. “None of us have a ton of experience of it.”

For many years, overtime ended as soon as one team scored. Then the rule was altered so both teams could possess the ball — unless the first team on offense scored a touchdown. In that case, the game would end on that TD, and that’s what happened when New England beat Atlanta 34-28 in Super Bowl 51.

An even more recent rule change mandated that in the postseason, both teams can possess the ball even if the first offensive team scores a touchdown. Now NFL playoff overtime even more closely resembles the college OT format, where teams alternate possessions. And in college, teams often like to have the ball second because they’ll have a better sense of what they need on their drive.

This time, Kansas City had that advantage, which meant the Chiefs had no choice but to go for it on fourth-and-1 from their own 34, down three. They converted and eventually reached the end zone on a 3-yard touchdown pass from Mahomes to Mecole Hardman.

“There’s two ways: You kick it off or you receive it,” Kansas City coach Andy Reid said. “I’m not sure there’s a right answer, necessarily. Ours ended up being the right one. That’s what we felt was the right thing to do.”

Reid’s comments suggest there’s no obvious consensus among coaches about what to do, but if the Chiefs had won the toss, they were prepared to kick off and play defense first.

“We talked for two weeks about new overtime rules,” defensive tackle Chris Jones said. “Give the ball to the opponent. If we score, we go for 2.”

One defense of San Francisco’s decision to take the ball involves what happens if the game is still tied after both teams have had a possession. Then, the game DOES become sudden death — so there’s a clear potential edge in having the ball third. If the game was still tied after the first two possessions, the 49ers could have gotten the ball and any score would have won it.

But overtime never made it that far.

“We went through all the analytics and talked to those guys,” Shanahan said. “We wanted the ball third. If both teams matched and scored, we wanted to be the ones with a chance to go win.”

Overtime can reach a third possession if each team kicks a field goal.

“We got that field goal, so we knew we had to hold them to at least a field goal,” Shanahan said. “And if we did, we thought the game was in our hands after that”

If each team scores a touchdown, then as Jones said, the second team could simply go for a 2-point conversion to prevent its opponent from getting the ball again.

It turned out Kansas City didn’t have to worry about any conversion because once the 49ers settled for a short field goal, the touchdown by the Chiefs won the game.

And Jones was a big reason it worked out that way. He came through unblocked on San Francisco’s last offensive play, forcing an incompletion that set up a short field goal by Jake Moody.