SANTA CLARA, Calif. — The San Francisco 49ers are hoping for a healthy and happy second half of the 2014 season.

They got the healthy part off on the right foot Wednesday in their first full practice after their bye.

For the first time all season, the 49ers had all 53 players on their active roster participating in their workout as they began preparations for Sunday’s rematch with the St. Louis Rams.

It couldn’t come at a better time, head coach Jim Harbaugh noted, given the recent struggles his club has had against the NFC West rival.

“It’s a salty opponent,” Harbaugh said. “You just turn on the film of all our games with the Rams and that speaks volumes.”

The 49ers beat the Rams 31-17 in Week 6, but the sweat level was much higher than the 14-point spread might indicate. The Rams got the 49ers’ attention by jumping to a 14-0 lead in the first quarter, and the win wasn’t assured until reserve cornerback Dontae Johnson returned an interception for a touchdown in the final minute.

As much as the scare and the win, that game is best remembered for the inordinate number of injuries the 49ers incurred. Guard Mike Iupati (concussion), inside linebacker Patrick Willis (toe), cornerback Chris Culliver (hamstring) and nickel back Jimmie Ward (quad) all missed the Week 7 loss at Denver because of injuries suffered against the Rams.

The good news: All four were back at practice Wednesday, aided in the recovery in no small part by last week’s bye.

By contrast, the Rams placed two players on injured reserve this week, had eight of 13 players on the injury report sit out Wednesday’s practice and will have made at least 19 roster moves involving 15 players this season by the time Sunday’s game starts.

Harbaugh saw the two trick plays the Rams converted against the Seattle Seahawks on special teams two weeks ago, and knows St. Louis head coach Jeff Fisher will throw out the kitchen sink to gamble on a potential victory.

“You’ve just got to be on high alert at all times,” Harbaugh said. “There’ll be an onside kick that comes when they’re up 14-0. There’s fakes in the punt return game. There’s fakes in the punt game, in the kickoff return. Makes us play at a higher awareness, high alert.”

SERIES HISTORY: 130th regular-season meeting. 49ers lead series, 64-62-3. The all-time series appeared headed for a 63-63 deadlock when the Rams stunned the 49ers by scoring the first 14 points in their Week 6 matchup in St. Louis. But the 49ers responded with 24 unanswered points and retained the series lead with a 31-17 victory. The 49ers haven’t lost to the Rams at home since 2007, but the 2010 (23-20 overtime win) and 2012 (24-24 tie) games were deadlocked at the end of regulation.

–RB Marcus Lattimore participated in his first regular-season practice with the 49ers on Wednesday. Lattimore is attempting to come back from a serious knee dislocation suffered in a game for South Carolina in 2012. The 49ers have three weeks to activate Lattimore or he will be declared out for the season.

–C Marcus Martin worked out with the first team Wednesday and is in line to make his first NFL start Sunday against St. Louis. Martin is replacing Daniel Kilgore, who underwent ankle surgery after getting hurt in the Week 7 loss at Denver.

–G Mike Iupati was cleared to return to the team after having suffered a concussion in the 49ers’ win over the St. Louis Rams in Week 6. Iupati practiced Wednesday and is slated to start Sunday in the rematch with the Rams.

–ILB Patrick Willis was a full participant at practice Wednesday, making him likely to return from a one-game absence to face the St. Louis Rams on Sunday. Willis suffered a toe injury in the Week 6 win over the Rams.

–ILB NaVorro Bowman recently clocked a 40-yard dash “in the 4.5 range,” according to 49ers general manager Trent Baalke. If so, that would be an indication Bowman’s recovery from off-season knee surgery is nearly complete. The 49ers hope to get Bowman back on the practice field sometime early next month.

–OLB Ahmad Brooks had two of the 49ers’ five sacks in their 31-17 win over the St. Louis Rams in Week 6. Brooks remains the 49ers’ best sack threat among linebackers with Aldon Smith still serving a suspension.

–CB Tramaine Brock took it easy at 49ers practice Wednesday as he nurses a toe injury that caused him to miss four games earlier this season. Brock returned to face Denver in Week 7 and is expected to start again Sunday against the St. Louis Rams.

–CB Chris Culliver returned to practice on a fulltime basis Wednesday after having missed the 49ers’ most recent game — Week 7 against the Denver Broncos — because of a hamstring injury. If Culliver is able to play Sunday against St. Louis, it will mark the first time the 49ers will have their top three cornerbacks available since Week 2.

–S Jimmie Ward was a limited participant at practice Wednesday. He is expected to play Sunday against the St. Louis Rams, but now the question is: Is he still the 49ers’ starting nickel back? With cornerbacks Tramaine Brock and Chris Culliver likely to start together for the first time since Week 2, the 49ers will be looking for a slot into which to place their impressive third corner, Perrish Cox. That could come at Ward’s expense.

MATCHUPS TO WATCH:

–49ers QB Colin Kaepernick vs. Rams defense. After a slow start, Kaepernick was borderline unstoppable when the 49ers rallied to beat the Rams 31-17 in St. Louis in Week 6. Kaepernick found three different receivers for touchdowns in the win while amassing his highest yardage total of the season (343) and second-highest passer rating (123.9). He also found time to record his highest rushing average of the season (12.3) while going for 37 yards on three runs.

–49ers pass rush vs. Rams offensive line. This could be a big-time mismatch. The 49ers sacked Rams quarterback Austin Davis five times in their 31-17 win in St. Louis in Week 6. Linebackers Ahmad Brooks and Dan Skuta had two sacks apiece in the win. Now, the 49ers figure to experience even less resistance from a Rams offensive line that’s missing several key players. That’s bad news for Davis, who completed only 21 of his 42 passes while running for his life in the first meeting, and had a last-minute interception returned for a touchdown that sealed the Rams’ fate.

–49ers special teams vs. Rams P Johnny Hecker. Hecker was quite busy in the Rams’ first game of the season against the 49ers, punting eight times for a fine 43.9-yard average. Actually, the plan was for Hecker to punt only seven times that day, but a designed fake on which Hecker was supposed to throw a pass was foiled by an alert play by 49ers CB Chris Cook. Hecker, a former high school quarterback, has thrown six passes out of punt formation in his career, completing five.