SANTA CLARA, Calif. — The St. Louis Rams had a season-high eight sacks and forced a fumble by quarterback Colin Kaepernick at the goal line with two seconds remaining, preserving a 13-10 victory against the San Francisco 49ers at Levi’s Stadium on Sunday.

Facing third-and-goal from the Rams’ 1, Kaepernick kept the ball on a quarterback sneak, but he fumbled, and the Rams recovered in the end zone.

Defensive end Robert Quinn had two of the Rams’ season-high eight sacks, six of which came in the first half.

The 49ers (4-4) lost their second straight game and fell three games behind the Arizona Cardinals in the NFC West.

Rams running back Tre Mason carried 19 times for 65 yards. Quarterback Austin Davis completed just 13 of 24 passes for 104 yards and one touchdown and was intercepted twice.

Kaepernick went 22 of 33 for 237 yards and one touchdown to wide receiver Anquan Boldin, who caught six passes for 93 yards.

After a scoreless third quarter dominated by defense, the Rams (3-5) and 49ers entered the fourth quarter tied 10-10.

With under eight minutes left, San Francisco’s Andy Lee shanked a punt from the end zone, giving the Rams a first down at the 49ers’ 29. The Rams moved only eight yards, but Greg Zuerlein kicked a 39-yard field goal with 5:25 left, staking the Rams to a 13-10 edge.

Each team went three-and-out, and San Francisco took over at its 12 with 3:11 remaining. Kaepernick hit wide receiver Stevie Johnson for 25 yards on first down. A holding penalty on Rams cornerback Lamarcus Joyner gave the 49ers a first down at the 50 with 1:58 left to play. After a penalty on San Francisco, Kaepernick fired a short pass to Boldin, who broke safety Rodney McLeod’s tackle and gained 20 yards.

Three plays later, Kaepernick threw a deep pass to wide receiver Michael Crabtree that fell incomplete, but Rams cornerback Trumaine Johnson was flagged for pass interference at the 5. A holding penalty on Johnson gave the 49ers first-and-goal from the 2.

Kaepernick completed a 1-yard pass to Crabtree before Kaepernick fumbled on third down and the Rams recovered in the end zone.

The 49ers took a 3-0 lead on Phil Dawson’s 34-yard field goal with 10:32 left to play in the first quarter, but the Rams pulled even on Zuerlein’s 37-yarder with 1:20 remaining.

The 49ers capitalized on a turnover to take a 10-3 lead on Kaepernick’s 27-yard touchdown pass to Boldin early in the second quarter.

Strong safety Antoine Bethea intercepted Davis’ underthrown pass intended for wide receiver Tavon Austin along the right sideline, giving the 49ers a first down at the Rams’ 35 and Boldin scored three plays later.

The Rams cashed in on a Kaepernick fumble late in the first half to pull even. Quinn sacked Kaepernick and stripped the ball, which defensive end Eugene Sims recovered at the 49ers’ 36.

Rams running back Benny Cunningham gained 17 yards on a screen pass. Two plays later, Davis hit a wide-open Kenny Britt on a shallow crossing pattern, and he jogged into the end zone, making it 10-all with 1:04 left in the half.

NOTES: Niners CB Tramaine Brock (toe) was inactive for the sixth time in the past seven games. … Niners ILB Patrick Willis (toe) was inactive for the second straight game. … Rams S Mark Barron, acquired Tuesday in a trade with Tampa Bay, made his debut for St. Louis. … WR Damian Williams, who was released last week by Miami and signed Wednesday with the Rams, made his St. Louis debut. … Rookie C Marcus Martin made his first career start for the 49ers, replacing the injured Daniel Kilgore. … Rams rookie Greg Robinson made his first career start at left tackle, replacing the injured Jake Long. Robinson, the No. 2 overall pick in the 2014 draft, started the previous three games at left guard. … Rams CB Trumaine Johnson played for the first time since injuring a knee in the third preseason game.