SANTA CLARA Defensive coordinator Vic Fangio thinks the 49ers' inside linebackers will have the toughest assignment on defense Sunday against the Texans, who are committed to the run, love play action and aren't shy about going downfield sometimes deep downfield to their tight ends.
Adding to the challenge is that Fangio isn't sure which of his linebackers will play.
Patrick Willis is making progress from the groin injury that kept him out of last week's game in St. Louis. Willis spent the beginning of Thursday's practice rehabilitating on a side field and is iffy for Sunday.
"I think Pat's getting a lot better, making great progress," Fangio said. "I think the chances are better than 50-50 (that Willis plays), but we don't know for sure yet."
Willis offered a similar assessment Wednesday. He said the groin injury, suffered Sept. 22 against the Colts, was the first he's experienced.
"Hopefully, I will be able to get out there," he said. "But it's still uncertain right now."
If the 49ers hold Willis out, Michael Wilhoite will make his second straight start next to NaVorro Bowman. Wilhoite said he's preparing as if he's starting, and he agreed with Fangio that the balanced Texans offense presents a difficult challenge.
Wilhoite said the Texans look for tight ends Owen Daniels and Garrett Graham not only in the short and intermediate passing game but also for big plays. Both average more than 10 yards a catch and they have six touchdowns between them.
"They're almost like receivers with blocking capabilities," Wilhoite said. "Which is tough because, since the beginning of time, that's always been known as a mismatch a receiver on a linebacker. It's something you don't want, and that's what they present."
Brock to play Fangio said Tramaine Brock would be the 49ers' No. 3 cornerback for at least another week as Nnamdi Asomugha continues to come back from a knee injury.
"He did a nice job," Fangio said of Brock's game against the Rams. "He probably had the biggest play of the game in breaking up that pass that Donte (Whitner) intercepted in the end zone. That was a third-and-1, deep into the second quarter. They were in field-goal range, and I think the score was only 7-3 at the time."
Brock likely will face the Texans' top wideout, Andre Johnson, when the 49ers are in their nickel defense.
"I like that matchup," safety Eric Reid said. "(Brock's) an aggressive cornerback, and he's not going to back down, by any means."
Et cetera Offensive coordinator Greg Roman suggested that wideout Jon Baldwin will get more snaps against Houston.
"I love to see guys play physical and make plays when opportunities come their way," Roman said. "I'm sure he'll be getting plenty of opportunities this week, and he's got to take advantage of them."
Fangio said it shouldn't only be defensive players who get fined for big hits on receivers. "I've always said when they're fining these people for these hits, they should be fining the quarterback for throwing these guys into those big hits," he said.
Right tackle Anthony Davis practiced on a limited basis Thursday after sitting out Wednesday's practice with a shoulder injury.