Gonzalez, 31, underwent an MRI test on Monday after he complained of soreness and has not participated in any Spring Training games. A second scan was ordered on Thursday and team medical director Dr. Tim Kremchek examined him after returning to town.
Shortly before the Reds made the announcement of the diagnosis, Gonzalez said he had a bone bruise. He had been walking around the clubhouse on crutches.
"[Kremchek] told me to rest," Gonzalez said. "I'll be on the crutches for a week to not put pressure on my leg. It was nothing serious. I'll just let it heal."
Even if Gonzalez is cleared to resume playing in three weeks, that would take him to March 21. The regular season opens only 10 days later on March 31.
"He'll need some time to get back into baseball shape," Krivsky said.
Last season, Gonzalez batted .272 with 16 home runs and 55 RBIs in 110 games. He was limited to pinch-hitting for much of September because of a bone bruise on the same knee.
"It's in a different spot," Krivsky said of the fracture.
The Reds signed Gonzalez as a free agent to a three-year, $14 million contract on Nov. 20, 2006.
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For now, the Reds will fill in at shortstop with what they already have in camp. Much of the playing time could go to Jeff Keppinger, who picked up the team when Gonzalez was often out last season.
Keppinger batted .332 in 67 games as a utility player. He started at five different positions in 2007, including 43 at shortstop. He doesn't have as much range as Gonzalez but committed only two of his errors at shortstop.
Other shortstop candidates in camp are Juan Castro, Paul Janish and Adam Rosales. However, Castro is coming back from August Tommy John right elbow reconstruction surgery. Neither Janish nor Rosales have any Major League experience.
"We'll see who plays the best and who we think can help us the most will be the one who goes and takes his place," manager Dusty Baker said.