Both struggling franchises come in with identical 1-5 records.
"He's a very bright young man, so he's a real quick study and his retention is outstanding," Bears offensive coordinator Terry Shea said of Krenzel. "That's a great starting point when you have a young rookie. It won't be a question of him not understanding or not knowing the material. It'll just be how many new experiences will he have as a young quarterback."
Krenzel, a fifth-round draft pick, came on in relief of Jonathan Quinn in last weeks' 19-7 loss to Tampa Bay. Krenzel was 9-of-19 passing for 69 yards and an interception. Krenzel did, however, guide the Bears to their only touchdown.
Krenzel was 24-3 as a starter with the Buckeyes, but the NFL is a whole other story. The 49ers will gear up to stop the run and make Krenzel beat them. Bears running back Thomas Jones is fifth in the NFC in rushing with 510 yards and five touchdowns, while averaging 4.4 yards per carry.
Shea said he'll call more plays to get Krenzel out of the pocket, utilizing his athletic ability. The Bears managed just 160 yards of total offense with Jonathan Quinn at QB against Washington two weeks ago, and just 167 last week against Tampa Bay.
The obvious problem is the lack of production at the quarterback position. But Shea wouldn't point fingers.
"We're stressing accountability to everybody on the offensive side of the ball," he said. "That was a big theme that I gave the offense (Wednesday) in our meeting.
"We've just got to play better as an offense. It's not necessarily only the quarterback that drives this train."
Key Matchups
Craig Krenzel, Bears quarterback
All eyes will be on the rookie from Ohio State, who will get his first career start. Krenzel was less than brilliant last week in relief duty against Tampa Bay, but he could solidify his future in Chicago as the long-term backup to Rex Grossman.
Tony Parrish, 49ers safety
The former Bear would like nothing more than to have a couple of picks against his old mates. Parrish tied for the NFL lead with nine interceptions last season during a breakout All-Pro year. The 'Niners will be throwing all sorts of different looks at Krenzel.
Another key matchup
Tim Rattay, 49ers quarterback
Rattay has been hot the last three weeks, completing 66 percent of his passes for 1,002 yards and five touchdowns. San Francisco's passing offense is ranked in the top 10 in the league, and Rattay, even with a sore forearm, has been sharp.
Alex Brown, Bears defensive end
With Adewale Ogunleye nursing a sore leg, Brown is the one guy who can cause havoc in the pocket. If the Bears are to get some turnovers in the secondary, it's gotta start with some pressure from Brown.