The St. Louis Rams perfectly executed a rare fake punt return for a 90-yard touchdown against the Seattle Seahawks on Sunday.

The Rams pretended to catch the punt on the left side of the field, but the ball was actually caught on the right side of the field. The Seahawks fell for it, running to the wrong side, and Rams returner Stedman Bailey was able to waltz into the end zone for a touchdown.

It was a brilliantly planned play, but there's one pivotal question: How did the Rams know where the Seahawks were going to punt it?

To pull this off, the Rams had to know the Seahawks were going to punt it to the right. The Rams faked out the Seahawks because the St. Louis players all ran to the left side of the field immediately after the ball was kicked. How did they know with certainty that the ball wasn't going to be there?

After the game, Rams players and coaches explained how they came up with the play. It turns out they installed the trick play on Thursday because they noticed on tape that Seahawks punter Jon Ryan almost always kicked it to the right side of the field when he was trying to pin teams deep.

Bailey told the St. Louis Dispatch:

Coach Bones (Fassel) saw the Bears try it a few years back — it worked for them, too, but it was called back on a penalty. He noticed that when (Seattle’s) punter tried to sky it, to pin us deep, the punt always ended up in pretty much the same spot.

Rams coach Jeff Fisher said there was a 90% chance that Ryan was going to kick it to the right on a punt from that distance, so he gave the play the green light.

The only way the Rams could have done this is if they knew where Seattle was going to punt it. And they did.

Fisher talked about the play at his news conference:

We executed it in practice. Johnny (Hekker) gave him a really good look. And the key is that (WR) Tavon (Austin) and (S) Cody (Davis) really oversell that the ball is going … the team is expecting the ball to come down to their left, our right. And so when they saw Tavon running over, they probably thought it was miss-hit. The downside was he doesn’t catch it, the ball goes in the end zone, it’s a touch back or it’s downed. The upside was we felt like if he was able to field it, then we had a chance to probably put points on the board. This is something, it’s a copycat league, OK. The Bears did this with (Devin) Hester against the Packers six or seven years ago and scored, but it was called back for holding. But we just felt, based on the information that we had and everything, we felt like … I had enough … it was an automatic based on field position as well. I told Coach Fassel to go ahead and run it if we had the right field position, and we did. So it worked. Special teams obviously played a big factor in this one.

Seahawks coach Pete Carroll said the Rams did "some unbelievable cool things" on special teams in the game, which is pretty accurate.

Here's the play again: