SANTA CLARA -- The 49ers are hoping other reinforcements soon step up and succeed the way Tramaine Brock did.

Filling in for Nnamdi Asomugha as the nickel back, Brock intercepted two passes and returned one for a touchdown to spark a 34-3 rout of the Houston Texans on Sunday night.

"When you play like that, you're going to continue playing," coach Jim Harbaugh said Monday of Brock's impending role. "There'll be more opportunities for him, and we're excited about that."

Also appealing to the 49ers is the imminent arrival of more reinforcements after the team has rebounded for a 3-2 record through a formidable early schedule.

Harbaugh expects four players on reserve/injury lists to start practicing next week, when they become eligible: wide receiver Mario Manningham (knee), cornerback Eric Wright (personal issue), rookie defensive tackle Tank Carradine (knee) and rookie nose tackle Quinton Dial (foot).

Wide receiver Michael Crabtree's recovery from a torn Achilles is progressing well enough that the 49ers are hoping he'll be ready to play next month. Crabtree, the 49ers' leading receiver last season, tore his right Achilles on May 21.

"Mid- to late November is what we're hoping for," Harbaugh said. "He seems to be on track for that. He's starting to run."

Crabtree has not commented publicly since the injury, but he has privately expressed optimism about his recovery and gratitude for the widespread encouragement he's received among his teammates and around the sports world.

"I talk to him every day, and things seem to be going well," Harbaugh said. "He's been very positive and upbeat."

Crabtree started the season on the reserve/physically-unable-to-perform list, meaning the 49ers can take him off it between next week and through Nov. 19 to begin practicing. A 21-day practice period follows, so the 49ers could delay his debut until Dec. 15.

No timetable officially has been shared regarding outside linebacker Aldon Smith's eventual return. Smith has been on personal leave for substance-abuse treatment for two weeks. Harbaugh said he and Smith have exchanged text messages, adding: "I heard things are going positive and very well."

Carradine and Dial would be much-needed additions for a defensive front that might be without end Ray McDonald, who sustained a biceps injury making a sack against the Texans and was undergoing an MRI Monday. Harbaugh was still awaiting those MRI results during Monday's noon news conference.

Carradine was a second-round pick, and Dial was a fifth-round choice who's gotten his weight up from a listed 318 pounds to 340 or 350 pounds, Harbaugh said.

The 49ers defense has done well the past two victories without three starters: Smith, inside linebacker Patrick Willis (groin) and nose tackle Ian Williams (season-ending ankle fracture). Asomugha was the No. 3 cornerback before hyperextending his right knee Sept. 22.

Brock, who set up a Donte Whitner interception Sept. 26 at St. Louis, produced the first two of the 49ers' four take-aways against the Texans.

"He's now getting an extended opportunity and making the most of it. Love to see it," Harbaugh said.

Sunday night's four take-aways nearly matched the 49ers' total (five) through the previous four games.

"That's really encouraging getting turnovers. We've been kind of down on getting turnovers," Harbaugh said. "Sometimes things start breaking right for you. Kind of like the olive jar. Everybody's familiar with the olive jar."

For those who aren't, here is "The Olive Jar," as told by James Joseph Harbaugh:

"Well, you open up a brand new can of olives. You turn it over, and no olives come out. They're packed in there so darn tight, but you can't get one to come out. Pluck one out of there and, whoosh, they want to come out, they're just flying out of the jar. Hopefully that's the case for us defensively."

With Sunday's three interceptions and fumble recovery, the 49ers now have as many take-aways as turnovers (nine apiece) this season. That zero turnover ratio ranks 18th in the NFL. In 2011, the 49ers committed 10 turnovers all season; they had none Sunday.