SANTA CLARA The 49ers are breaking in a new Swiss army knife.
In recent seasons, that was the description coach Jim Harbaugh gave to Delanie Walker, who was part tight end, part fullback, part wide receiver in the 49ers' offense and who finished fifth on the team in receiving yards last season.
Walker is now with the Tennessee Titans, which means his unique, multifaceted role had to be taken on by others, mostly fullback Bruce Miller. Walker was on the field for 57 percent of the plays last season. Miller has been in on 53 percent of the snaps through the first four games and has been lining up in many of the spots Walker once occupied.
"Bruce is like our Swiss army knife. He does everything from special teams to everything on offense," quarterback Colin Kaepernick said this week. "Whether it's blocking, running, catching passes, he's someone that really makes this offense go, and he's a vital part of it.
"So as he develops, and as he continues to get better, our offense will continue to get better as well."
Like a number of offensive players, Miller struggled during the 49ers' two-game losing streak. And it was no coincidence that the 49ers signed another fullback, Owen Marecic, during that stretch.
But Miller bounced back strong last week against the Rams. He blazed ahead of Frank Gore on all of Gore's longest runs, including the fourth-and-1 play when Gore raced into the end zone for a 34-yard touchdown.
A few days later, the 49ers released Marecic.
Miller also has had a bigger role in the passing game than he did during his first two seasons when Walker was around. Kaepernick usually makes a short throw to the fullback early in games to help the quarterback find a rhythm.
Miller caught three passes for 22 yards against the Rams, and he has eight catches for 78 yards on the season. The eight receptions are one fewer than the team's No. 2 wide receiver, Kyle Williams.
The 49ers converted Miller from college defensive end to fullback when they drafted him in 2011. But he said he played tight end and baseball in high school, so catching a ball isn't all that foreign to him.
"It's pretty cool," Miller said of his increased role in the passing game.
"Especially if it's helping. Moving the chains, third and short I want to be effective. I don't want to catch balls just to catch balls. I want to be able to help the team."
The 49ers used a second-round draft pick in April on tight end Vance McDonald. At 6-foot-4, 270 pounds, McDonald is much bigger than Walker. He has four catches for 59 yards and is averaging nearly 15 yards a catch. The team's third tight end, Garrett Celek, is mostly a run blocker. He has one catch for 30 yards this season.
McDonald still is rounding into form as a blocker, which was Walker's specialty. And that's why most of Walker's former snaps have been going to a fullback.
Miller, who also plays on special teams, said his body still is adjusting to his added responsibilities. He said the Rams game was the first time this season in which he's felt good physically by the end of the game.
"I felt like I still had a second wind," he said. "Felt better. Felt good."
Et cetera Linebacker Patrick Willis (groin) was limited in practice Friday for the third consecutive day and is listed as questionable on the 49ers' injury report. If he can't play, Michael Wilhoite will make his second straight start.
Houston's inside linebacker, Brian Cushing, has been cleared to play after suffering a concussion in the fourth quarter of Sunday's loss to the Seattle Seahawks. Cushing leads the Texans in tackles.
Ray Wersching will be an honorary captain Sunday. The 49ers are commemorating the field goal Wersching kicked on Dec. 7, 1980, to cap a 28-point, come-from-behind win against the Saints.
Read Matthew Barrows' blogs at www.sacbee.com/sf49ers and listen for his reports Tuesdays on ESPN Radio 1320.