SANTA CLARA, Calif. — The San Francisco 49ers have totaled only 33 points the past two weeks against the two worst teams in the NFC East.

They have allowed an opposing running back to gain more than 100 yards in two of their past three games.

They have not won at home by more than five points all season, and in fact have been beaten twice at Levi’s Stadium by clubs with losing records.

So what makes the 49ers optimistic on the eve of their most important game of the season — Thursday night’s visit by the Seattle Seahawks?

Well, two things actually.

First off, the 49ers have faced self-imposed “must-wins” in each of their three games since losing to the St. Louis Rams at home on Nov. 2. They have won them all.

But most important, Aldon Smith is back.

Even though he was playing for just the second time since serving a nine-game suspension, Smith stamped himself in midseason form Sunday, contributing two sacks and an ever-presence in the Washington Redskins’ backfield during the 49ers’ 17-13 home win Sunday.

“I thought he played outstanding. He really had the speed, had power,” 49ers coach Jim Harbaugh gushed after the game. “I think (Smith’s presence) helps everybody. Helps us, yes. I don’t think I’m going too far out on a limb by saying that.”

Smith had six hits on Washington quarterback Robert Griffin III. Two produced sacks. The other four helped convince the Redskins to attempt only 19 passes.

Up next: the ultimate challenge of facing the defending champs. Despite playing 52 of the team’s 55 defensive snaps Sunday, Smith pronounced himself ready for the test.

“I don’t have as many hits on my body as the guys who have been playing,” he noted. “So hopefully that comes into play on Thursday.”

MEDICAL WATCH: ILB NaVorro Bowman will not practice with the team this week, 49ers coach Jim Harbaugh announced Monday. The plan is for Bowman, who underwent major knee surgery at the end of last season, to work out with the training staff again this week in hopes of being able to take the practice field with the team next week.

Bowman visited Dr. James Andrews over the weekend. No results of that examination were made public.

“Yeah, (we’ll) take it week-by-week with NaVorro. And, this week will be another week of rehabilitation and continuing to do what he’s been doing,” Harbaugh said. “Don’t anticipate any practice for him this week.”

–WR Bruce Ellington missed his second consecutive game Sunday because of a sprained ankle. He was replaced on punt returns by Perrish Cox and on kickoff returns by Carlos Hyde.

–OT Anthony Davis did not play in Sunday’s win over Washington after having suffered a concussion a week earlier against the New York Giants. 49ers coach Jim Harbaugh reported Monday that Davis was still experiencing symptoms of the concussion, making him very questionable for Thursday’s showdown with Seattle.

REPORT CARD VS. GIANTS

PASSING OFFENSE: C-minus — On the surface, Colin Kaepernick’s numbers look pretty good: 20-for-29, 256 yards. But bottom line: Those numbers produced a total of just 17 points in a narrow win against a last-place team, and Kaepernick’s one touchdown pass was offset by an interception. As usual, Anquan Boldin was great, Michael Crabtree mediocre and Vernon Davis a non-factor.

RUSHING OFFENSE: D-minus — The 49ers’ two best runs came at critical times when Frank Gore got a first down on fourth-and-1 in San Francisco territory late in the game and Carlos Hyde scampered in for the game-winning touchdown a couple of minutes later. Other than that, there was a lot of nothing … other than a fumble apiece by Gore and Hyde that helped keep the Redskins in the game. Even Kaepernick (nine attempts, 14 yards) was no help in the running game.

PASSING DEFENSE: A — The 49ers held Robert Griffin III to 106 passing yards and sacked him five times. They also limited dangerous wideouts DeSean Jackson and Pierre Garcon to five harmless catches. And to put a bow on a near-perfect performance, they sacked Griffin on Washington’s final play of the game, forcing a fumble that Ahmad Brooks recovered to seal the win.

RUSHING DEFENSE: C-plus — For the second time in three games, the 49ers allowed a 100-yard rusher in Washington’s Alfred Morris. At least the hard-running Redskins back had to earn his 125 yards on 21 carries. And while Morris had a 30-yard run and a short touchdown plunge, he was almost totally ineffective on third down as the 49ers forced eight Redskins punts.

SPECIAL TEAMS: A — It’s hard to find any fault on a day when: Phil Dawson made all three of his kicks (two extra points and one field goal), Andy Lee averaged 50.3 yards on six punts and backup return men Carlos Hyde and Perrish Cox kept from making the one critical mistake that could have turned a close game in the other direction.

COACHING: C-minus — Give Jim Harbaugh credit for having the guts to go for it on fourth-and-1 in his own territory in the fourth quarter. The first down led to the 49ers’ game-winning touchdown. But a narrow home win over a last-place team that got blown out last week at home by another last-place team was far less than what had been expected.