When the Los Angeles Rams visit the San Francisco 49ers on Monday night at Levi's Stadium in Santa Clara, there will be so many major narratives surrounding this game that the key one is often lost in translation.

The Rams are back in Southern California after a 21-year stay in St. Louis. One of the most storied rivalries in football has come full circle to renew a once torrid intra-state rivalry between teams that were once the strength of the NFC West.

Ultimately, the Rams would have loved to open at home, but due to a scheduling conflict with the University of Southern California, the game is in the Bay Area as the second half of a Monday Night Football doubleheader. Kickoff is 10:20 p.m. ET.

A few months ago, this game looked like it would feature 49ers quarterback Colin Kaepernick and Rams No. 1 draft pick Jared Goff. But both will be on the sidelines as controversial backups.

Kaepernick received significant publicity the last two weeks for his action of sitting during the national anthem. However, lost in all the hyperbole is the play of starting quarterback Blaine Gabbert. Even before all the national media attention, which had nothing to do with on-the-field play, Gabbert won over the San Francisco locker room and head coach Chip Kelly.

"The whole body of work from April until today," Kelly said when asked what impressed him about Gabbert. "He's a good fit for what we want to get accomplished, and I have a lot of confidence in what he can do for us offensively."

Kelly said Gabbert was "very matter of fact to him," about getting the news that he was named the opening-day starter, "and let's go to work."

Gabbert's best game of his NFL career came against many of the same defensive players he will face Monday night.

In the 2015 season finale, the 49ers signal-caller threw for 354 yards and helped beat the Rams, 19-16. The defensive backfield of cornerback Trumaine Johnson, cornerback E.J. Gaines, safety T.J. McDonald and safety Maurice Alexander will need to play sound techniques and limit the deep-ball opportunities of Gabbert to wideout Torrey Smith. Smith is a true deep threat and has the speed to get behind a nicked-up Gaines. Look for cornerback Lamarcus Joyner to play a significant role if Gaines struggles in coverage.

The Rams' front defensive seven is as good as there is in the NFL. The 49ers' offensive line is a middle-of-the-road unit. The Rams defense should be looking to control the 49ers rushing attack of Carlos Hyde and force Gabbert to make throws outside the pocket.

Rams defensive tackles Aaron Donald and Michael Brockers need to be able to control the interior of the offensive line. If this duo can get Hyde, who likes to run with vertical power, to play laterally, this will allow new middle linebacker Alec Olgetree to use his speed to stop the run game.

A key matchup in this game for the 49ers offense and the Rams defense is left tackle Joe Staley going against defensive end Robert Quinn. Five and half of Quinn's 50 career sacks have come against San Francisco. Most of those sacks have been against Staley, who is one of the most technically-sound players in the NFL and will need to play his best against the Rams.

The Rams' quarterback situation is another key to the game, but that narrative is a long way from being written. The Rams gave up six draft choices to select quarterback Jared Goff, who begins the season as a third stringer. Goff, the rookie from California, will spend the first game of his NFL career in street clothes.

"He's not ready, but he's really, really made significant progress," Rams head coach Jeff Fisher said of Goff.

While Goff seems upbeat and willing to learn, the Rams made the move to mortgage the franchise because they believed the signal-caller could start from Day 1. Instead that honor goes to veteran quarterback Case Keenum.

No matter who the Rams start at quarterback for the opener, or for the rest of the season, the offense begins and ends with running back Todd Gurley. The second-year man out of Georgia tore up NFL defenses in 2015 and will be looking to add to his career totals after being healthy all offseason. The Rams will look to pound the football off-tackle behind right tackle Rob Havenstein and left tackle Greg Robinson.

The 49ers' defensive front comes into the season with major question marks. The unit already lost starting nose tackle Ian Williams for the season with an ankle injury. Starting defensive end Arik Armstead and key backup at nose tackle Glenn Dorsey are currently nursing injuries. The Rams' offensive line needs to attack rookie defensive end DeForest Buckner and see if the young player can hold his own in the NFL.