The move to the West Coast has done wonders for the Rams.
Tavon Austin returned a punt 47 yards to set up Case Keenum's 4-yard touchdown pass to Brian Quick with 2:36 to play, and Los Angeles improved to 3-1 for the first time in a decade, adding to Arizona's early season woes with a 17-13 victory Sunday.
After years of mediocrity in St. Louis, the Rams are 3-1 for the first time since 2006, tied with Seattle for first in the NFC West.
The Cardinals (1-3), the reigning NFC West champions and expected to contend for the Super Bowl, have lost as many games this year as they did all of last season, and two of them have been at home.
Now they head to a Thursday night game in San Francisco almost certainly without Carson Palmer, who left late in Sunday's loss to undergo the concussion protocol after his head was slammed to the turf on a sack by Aaron Donald.
"The sky is not falling for us," Arizona coach Bruce Arians said. "I'm sure it is for a bunch of the fans - we're as disappointed as they are - but we've got a game Thursday night."
Keenum threw two touchdown passes to Quick, including a 65-yard score in the first quarter.
"Good teams win the close games," Keenum said. "It says we are fighters. We have done it on the road two times in a row. We are not going to dwell on where we are. We are looking ahead. We are looking at where we are going."
The play that sent Palmer to the sidelines forced a punt and Austin raced past would-be tacklers to the Arizona 34. A facemask penalty against Ifeanyi Momah moved the ball to the 19 and the Rams (3-1) went ahead when Quick caught a pass under tight defense for the score.
Arizona backup Drew Stanton was intercepted twice in the final minutes, including on a Hail Mary on the game's final play.
Arizona outgained the Rams 420-288 but committed five turnovers to the Rams' one.
"The big thing for us was getting the turnovers," Rams coach Jeff Fisher said. "Then, offensively we are improving in the third-down area and keeping the ball alive."
The Cardinals took their only lead of the game 13-10 on Chandler Catanzaro's 21-yard field goal on the final play of the third quarter.
Arizona had tied it at 10 on Palmer's 5-yard touchdown pass to Michael Floyd with 24 seconds left in the second quarter.
The Cardinals' offense stumbled through most of the first half and was hearing boos from the home crowd before finally getting moving in the final two minutes.
Quick caught only 10 passes for 102 yards and his future with the team was in doubt in training camp.
"When someone doubts you of course you are going to be motivated to prove them wrong," he said. "You have to fight and be strong mentally. If they (his coaches) feel like things are a little shaky that means you have to do something better. There were some things I had to do. I had to improve and get better. `'
A defensive holding penalty against the Cardinals kept the Rams' first scoring drive alive and an offensive holding penalty nullified an Arizona touchdown moments later.
The defensive hold on Patrick Peterson came when Keenum was sacked on third-and-five. Three plays later, Keenum connected with Quick for the long TD.
The Cardinals drove to the Los Angeles 10 on their next possession and Chris Johnson ran for an apparent touchdown. But a holding penalty against Jermaine Gresham nullified the score and the Cardinals settled for a field goal.
Another Arizona threat ended with a spectacular interception by Trumaine Johnson in the end zone.
Turnovers scuttled two Arizona scoring threats.
The Cardinals were at the Rams 33 in the second quarter when Palmer threw deep and Johnson intercepted in the corner of the end zone.
In the third quarter, Arizona recovered Keenum's fumble and drove to the Los Angeles 26, but Aaron Donaldhit Palmer, forcing a fumble that the Rams recovered.
Cardinals wide receiver Roy Green was inducted into the team's Ring of Honor at halftime.
Green played on offense, defense and on special teams in 12 seasons with the Cardinals (1979-90). He ranks second in franchise history in touchdowns, third in all-purpose yards and fourth in 100-yard receiving games.