Johnson picked up 170 yards from scrimmage and scored two touchdowns, making the St. Louis defense look helpless in the process.
Although, the defense cannot be solely blamed, as the offense contributed to the loss with a Benny Cunningham fumble and a missed field goal. The two mishaps knocked 10 points off the board, which turned out to be the difference of the game.
There were some positives on offense, such as rookie back Zac Stacy, who had another monster performance with 178 yards from scrimmage and two scores.
Also, Clemens was much better this week with 210 passing yards, one touchdown and zero picks, but a fourth-quarter fumble that set up a Titans touchdown spoiled his effort.
Overall, it was another admirable effort that was not rewarded with a victory.
Here are my takeaways from this game...
The defense certainly deserves its share of the blame, but it's hard to overlook the Benny Cunningham fumble and Greg Zuerlein missed field goal in the first half.
Those miscues lost the Rams 10 points on offense, which turned out to be the difference in the game.
Also, there was the Kellen Clemens fumble that gave Tennessee prime field position and resulted in a touchdown.
If the Rams could wipe out those three plays, they would have won this game by three scores.
The offense is in a desperate state with Clemens leading the way, so the team cannot afford to have these missed opportunities. It absolutely cannot happen.
The Rams entered the season without veteran Steven Jackson, and the team made no real effort to replace him with a high-profile name.
Fans thought the Rams were crazy for entering the season with second-year players Isaiah Pead and Daryl Richardson along with rookie fifth-round pick Zac Stacy, but clearly the coaching staff had faith in the youngsters.
That faith has paid off, as Stacy has established himself as a reliable, every-down back.
Stacy had 124 rushing yards and two touchdowns. This was his second-consecutive 100-yard game, and he now has 475 rushing yards in just four starts.
Stacy had been a pleasant surprise (one of the few from this season) and gives St. Louis the freedom to focus on other positions in the upcoming draft.
Barring injury, Stacy has all but secured his job as the starter for the remainder of 2013 and beyond.
The Rams have failed to meet expectations this season, so it's understandable that the coaching staff has received criticism for play-calling and personnel decisions, but the staff has done an admirable job getting the team ready to play without its starting quarterback.
The Rams were expected to roll over and play dead after Sam Bradford's injury, but that has not been the case. The team has been competitive and has been in a position to win games.
The team has lost both games in the post-Bradford era of 2013, but the team is playing with a lot of passion.
It's hard to believe that we'd see this same effort and performance without the presence of Jeff Fisher and his veteran coaching staff.
If you're going to point out the faults of the coaching staff, at least recognize the positives.
Early in the season, Tavon Austin saw a number of his promising punt returns called back due to penalties, and the misfortunes are still piling up.
Late in the second quarter, Austin blew by the defender and was wide open for a would-be touchdown, but Clemens overthrew him.
Had the quarterback hit Austin in stride, he would've easily been gone for a long touchdown.
Austin hasn't been lighting up the highlight reels with big plays this season, but the opportunities have certainly been there for the taking.
As Bernie Kosar so bluntly pointed out, Clemens was a disaster in the preseason with a 48.9 percent completion rate and four interceptions.
It was a bit surprising when Clemens was handed the No. 2 job over second-year player Austin Davis, who was the fan favorite, but the coaches liked Clemens for his experience in the Brian Schottenheimer system.
Regardless of his perceived faults, Clemens has done an admirable job stepping in for the injured Sam Bradford.
Clemens had two picks and completed less than 50 percent of his passes in his debut against Seattle, but he still put the team in a position to win the game.
This week, he improved on his accuracy, completing 57.1 percent of his throws. He also led the Rams to three touchdown drives and avoided throwing a pick.
He did have the fourth-quarter fumble that helped Tennessee put the game away, but he was still much better this week.
Clemens may not be ideal, but he's keeping the Rams competitive, which is all you can ask from a backup. With that in mind, he'll likely be under center for the remainder of the season.
Greg Zuerlein missed his only field goal attempt against Tennessee and has now missed his last two attempts overall.
Zuerlein was a perfect 14-for-14 to start the season, but he's once again becoming wild and erratic with his kicks.
We saw Zuerlein hit a similar wall as a rookie last season—he nailed his first 13 attempts of the 2012 season only to miss eight of his final 18 attempts.
With a backup quarterback leading the way, the Rams cannot afford to have missed field goals. Zuerlein needs to work out the kinks and have a strong second half of the season.
If there was one thing we could count on when it came to the 2013 Rams, it was their stout defense.
As of now, the Rams have fielded a middle-of-the-pack defense at best. The unit has been a liability more than strength, which is highly disappointing considering the group's level of talent.
Specifically, the run defense has been more troubling than any other aspect.
The Rams entered this game ranked 22nd in run defense (116.1 yards per game), and that ranking will surely drop following Johnson's 150-yard performance.
The Rams have allowed the opposing team's top running back to exceed 100 yards in four of their nine games this season.
With all the money and draft picks invested in top-notch talent, such as Chris Long, James Laurinaitis, Robert Quinn, Michael Brockers and Alec Ogletree, you'd think the defense would rank among the best in the league, but they have underperformed.
The front eight's inability to stop the run against Tennessee cost the Rams the game, and that's unacceptable.
During Janoris Jenkins' rookie campaign, the Rams could always count on the cornerback to step up and make a game-changing play when they needed it most.
This year, Jenkins has not only failed to make the big plays, but he's also been a liability on the field.
Rather than jumping routes and taking interceptions in for a score, Jenkins has been blowing coverage and missing tackles.
Where is Jenkins?
He was expected to take the next step as a player this season and become one of the elite NFL corners, but he has been an absentee player in 2013.