On the most important play of the game of San Francisco's Week 16 win, Rams cornerback Jalen Ramsey let 49ers wide receiver Emmanuel Sanders run right past him on the line of scrimmage.

Seconds later, Ramsey was chasing Sanders down from behind, after the latter had hauled in a 46-yard reception on third-and-16, setting up a game-winning field goal for Robbie Gould.

At first glance, it appeared Ramsey was to blame for allowing Sanders to get so wide open. But in reality, it actually was by design.

The play was designed for Ramsey to play a trail technique, where he would intentionally allow the receiver to get past him so that he would be able to jump anything underneath. The trail technique only works, however, when there's a safety over the top to cover the deep ball. That was Taylor Rapp's responsibility, and the rookie showed his inexperience in turning the wrong way, allowing Sanders to break free inside.

After the game, Ramsey didn't shy away from pointing the finger.

Rams cornerback Jalen Ramsey after losing 34-31 to the Niners. pic.twitter.com/euSiIYoqab — Lindsey Thiry (@LindseyThiry) December 22, 2019

"We was in a form of two-man," Ramsey described. "We had an adjustment check to it because they [were in] condensed splits. I played my technique, trusting that [Rapp] was going to be over top. He wasn't."

By defeating the Rams, the 49ers officially eliminated Los Angeles from playoff contention. Ramsey, who was acquired in a mid-season trade, clearly was frustrated by that development, and might have thrown the second-round pick under the bus as a result.

[RELATED: Where 49ers stand in NFC playoff picture after beating Rams]

It would seem, though, that Ramsey's brief time in Los Angeles thus far hasn't gone the way he had hoped, and therein lies the problem for the Rams. They traded away their own first-round picks in the next two drafts, as well as a fourth-round selection in 2021 to acquire him, and you don't pay that kind of price for a rental. Ramsey, though, will be on the final year of his contract next season and will be due to hit unrestricted free agency in 2021. Whether it's the franchise tag -- which would not go over well with Ramsey -- or a lucrative long-term deal, Los Angeles has already committed itself to the standout cornerback for the foreseeable future.

When you consider that the Rams' draft cupboards essentially are bare and they're about to enter salary-cap hell -- that's what happens when you bank on the wrong QB -- an unhappy team leader (who knows he has all the leverage) could create a troublesome situation. Just ask the Jaguars.

Jalen Ramsey blames teammate for blown coverage on 49ers' Emmanuel Sanders originally appeared on NBC Sports Bay Area