The Los Angeles Rams overcame the San Francisco 49ers 12-6 in a rain-affected game to boost their NFL play-off hopes. With the game tied at 6-6 in the fourth quarter, rookie kicker Joshua Karty drilled a 27-yard field goal to put the Rams ahead by three. Karty then capped off a final drive with his fourth field goal with 18 seconds remaining. On a disappointing night for the 49ers, De’Vondre Campbell refused to come on in the second half when asked to replace fellow linebacker Dre Greenlaw, who was experiencing foot soreness. Campbell, 31, had made 12 starts in 13 games, but Greenlaw – making his first appearance after recovering from an Achilles tendon tear he sustained during their Super Bowl defeat in January – was chosen ahead of him on Thursday. “He said he didn’t want to play,” said San Francisco head coach Kyle Shanahan, adding that Campbell gave no reason for his refusal. “That’s somebody who doesn’t want to play football, that’s pretty simple.” Tight end George Kittle said his team-mate’s actions were “immature”. Neither side scored a touchdown at a sodden Levi’s Stadium in California – the first game of the season without a touchdown. “This team can win a variety of ways,” said Rams coach Sean McVay. “I thought the defence came up big, time in and time out.” San Francisco opened the scoring in the first quarter with a 53-yard field goal from Jake Moody, before he added to his tally early in the third to give the 49ers a 6-3 advantage. But with the game level halfway through the third quarter, Niners wide receiver Deebo Samuel, who had recently complained on social media that he was not getting the ball enough, ended up dropping it during a key play, leading to boos from the home crowd. The defeat was an eighth in 14 games for last season’s beaten Super Bowl finalists, a further blow for their already slim play-off chances. While San Francisco struggle, the Rams have won eight and lost six of their games.