"Our quarterback has got to take better care of the football," McVay said tersely after the game.
Jared Goff produced three turnovers against the 49ers in what has become a growing trend for the fifth-year quarterback over the past four games.
"We're not taking good enough care of the football and that's something that's got to change, otherwise I'm going to continue to sit up here and say this week in and week out," McVay said. "It just can't continue to happen."
The Rams had a total of four turnovers, including a lost fumble by running back Malcolm Brown on the Rams' opening drive.
"It comes down to us executing and ultimately myself executing and taking care of the football and throwing it where it needs to be thrown and being smart with it," said Goff, who has four seasons remaining on a $134 million extension that included $110 million guaranteed.
Goff has had three games with multiple turnovers since a Week 8 28-17 loss to the Miami Dolphins, when he threw two interceptions and was strip-sacked twice.
This season, Goff has thrown 10 interceptions and has lost four fumbles. His 14 turnovers rank as the second most in the NFL, tied with Minnesota Vikings quarterback Kirk Cousins, and a spot behind Philadelphia Eagles quarterback Carson Wentz, who has 18 turnovers.
"They're all different," Goff said about his giveaways. "At the end of the day, they need to be eliminated. I don't think there's one thing that needs to stop, it just needs to be a little bit smarter with the ball and better decision-making."
McVay didn't hesitate to provide a variety of suggestions to cure Goff's ball-security issues.
"It might be keeping two hands on the ball, it might be that if somebody is swarming around you that you can't just throw it away when you don't see where you're going, being able to trust your guys to separate," McVay said. "But overall, any time that you turn it over as many times as we did and he did, it's just got to be better. He's capable of it, but we just got to be able to get it done."
The Rams' defense produced three turnovers and a touchdown, but it wasn't enough to overcome the offensive woes as Goff completed 19 of 31 passes for 198 yards, with two interceptions. He had a 52.9 passer rating.
In the first quarter, Goff threw a pass directly to 49ers cornerback Richard Sherman, who easily came away with the interception. Then with less than a minute to play in the half, the Rams trailing 7-3, Goff scrambled 3 yards before defensive back Jimmie Ward tackled him and knocked out the ball. And Goff fared no better after halftime, as rookie defensive tackle Javon Kinlaw intercepted a pass and returned it 27 yards to give the 49ers a 14-3 lead.
Goff has had an especially difficult time recently handling pressure, according to ESPN Stats & Information. He has thrown six interceptions under pressure this season -- including Sunday's third-quarter pick, which is tied with Wentz for the most in the NFL.
The defeat drops the Rams to 7-4 and served as their fourth straight loss to Kyle Shanahan and the 49ers, who improved to 5-6.
"We're not going to win many games when we take care of the football like that, so give them credit," McVay said. "But in a lot of instances we didn't do enough to win the football game, I don't care who you're playing."