In the lead-up to their rematch against the San Francisco 49ers, the St. Louis Rams were scrambling to find enough healthy players.

Disorganized? Well, not quite.

A disruptive defense they'd been waiting for all season led the way in an unexpected 13-10 victory at San Francisco on Sunday.

The Rams (3-5) had eight sacks, plus came up with the big goal-line stand at the finish that made up for an offense that mustered just 193 yards.

Rookie Aaron Donald and fellow tackle Kendall Langford led the push that led to Colin Kaepernick's lost fumble on a quarterback sneak at the goal line in the final seconds.

"It's great to find a way to win, but it's also great to know we didn't play our perfect game," guard Rodger Saffold said. "Our defense played a hell of a game. At the end, we found a way to win. That was awesome."

The bottom line is they've got momentum for Sunday's game at NFC West-leading Arizona, and coach Jeff Fisher is optimistic cornerback Janoris Jenkins will be back after missing two games with a knee injury.

Robert Quinn had two sacks for St. Louis, which totaled six sacks in the first seven games. The pressure led to the 49ers converting just three of 12 on third down.

"We were just getting after it," Donald said. "We were rushing the passer like we know how."

Expectations were low given Fisher and general manager Les Snead made 18 personnel moves over a 48-hour period in the middle of the week.

"It was a bounce-back effort all week long," Fisher said. "Things didn't look good early in the week. We got 'em back."

Earlier in the season, the 49ers erased an early two-touchdown deficit and won by two touchdowns in St. Louis. The Rams had 13 players on the injury list all week, many of them starters.

"Well, Wednesday we couldn't even practice. We had to kind of have a walkthrough day and try to get guys healthy," quarterback Austin Davis said.

"It wasn't a pretty win, but it's a great win."

The Rams shut out the 49ers in the second half, reversing a troubling trend. They were blanked 24-0 after the break last week at Kansas City and have been particularly weak in the third quarter, getting outscored 69-13.

Though St. Louis made little happen offensively, the 49ers were stopped, too.

Before gaining 59 yards on the final drive, San Francisco had mustered four first downs in four second-half possessions.

"I'm sure that every D-lineman expects to get multiple sacks game in and game out," Quinn said. "But of course, they don't come that easy.

"Guys were working their butts off and sold out for the team."

Until the finish when he was whistled for penalties on consecutive snaps near the goal, Trumaine Johnson had a strong season debut coming off a preseason knee injury. Johnson's return helped compensate for Jenkins' absence, and for Marcus Roberson's struggles.

Running back Zac Stacy again was the odd man out in a crowded backfield, and was the lone St. Louis player who didn't play. Stacy just missed 1,000 yards rushing his rookie season, but has fallen behind rookie Tre Mason and Benny Cunningham.

"Zac has handled this professionally," Fisher said. "He will get to play, he will get his reps. It's hard to spread the ball around."

Mason, a third-round pick, made his first career start and had 19 of the 27 carries, totaling 65 yards with a 3.4-yard average.

Fisher didn't exactly anoint Mason as the starter this week at NFC West-leading Arizona.

"You guys come out to Arizona, watch the first play and figure out who's going to start," the coach said.

___

AP NFL website: www.pro32.ap.org and http://twitter.com/AP_NFL