ST. LOUIS — The Monday night lights sure agree with the San Francisco 49ers.

Quarterback Colin Kaepernick threw for three touchdowns and 343 yards as San Francisco overcame a 14-0 first-quarter deficit for its seventh straight Monday night win, a 31-17 verdict over the St. Louis Rams at the Edward Jones Dome.

Kaepernick gave the 49ers their first lead with 9:58 left in the third quarter, avoiding a sack and rolling to his left before flinging an 11-yard scoring strike to wide receiver Anquan Boldin.

Kaepernick added his third touchdown pass with 13 seconds remaining in the period, hitting wide receiver Michael Crabtree on a 22-yard dart over the middle. Kaepernick connected on 22 of 36 attempts.

It was the third straight win for San Francisco (4-2), which jumped over Seattle for second place in the NFC West. But it came at a cost as the 49ers lost linebacker Patrick Willis (toe), left guard Mike Iupati (concussion) and backup free safety Jimmie Ward (quad) to injuries.

St. Louis (1-4) dropped its third straight game and fell to 0-3 at home. After throwing for 103 yards and a score in the first quarter, quarterback Austin Davis finished just 21 of 42 for 236 yards, getting sacked five times.

Placekicker Greg Zuerlein hit a 38-yard field goal with 2:24 left to pull the Rams within seven. St. Louis got the ball back with 1:05 remaining at its 9, but cornerback Dontae Johnson intercepted Davis and returned it 20 yards for a clinching touchdown with 53 seconds left.

The Rams started the game with an 11-play, 80-yard touchdown drive, scoring when running back Benny Cunningham ran a yard off left tackle on third-and-goal with 7:55 left in the first quarter.

St. Louis made it 14-0 with 53 seconds remaining in the quarter when Davis hit tight end Lance Kendricks with a 22-yard scoring strike off play-action. It came four plays after San Francisco tight end Vance McDonald fumbled to linebacker James Laurinaitis after a hard hit by free safety Rodney McLeod.

Placekicker Phil Dawson got the 49ers on the board with 7:07 left in the first half, drilling a 54-yard field goal.

San Francisco stunned the St. Louis portion of the bipartisan audience with 14 seconds remaining before halftime. Kaepernick lofted an 80-yard touchdown pass to wide receiver Brandon Lloyd, who ran past cornerback Janoris Jenkins, to slice the Rams’ halftime lead to 14-10.

NOTES: San Francisco TE Vernon Davis (back) was able to play, but starting RT Anthony Davis (knee/ankle) and CB Tramaine Brock (toe) were inactive. … St. Louis LG Greg Robinson, the No. 2 overall pick in this year’s draft, made his first start. Rodger Saffold moved to right guard, and Davin Joseph didn’t start after getting the call in the first four games. … The Rams paid tribute to the 1999 team that won Super Bowl XXXIV, wearing that year’s uniforms and honoring several members of that squad.