Ford underwent an MRI on Saturday, a day after leaving Oakland's 31-24 preseason loss to the Arizona Cardinals in the first quarter.
Ford missed six games last season for the Raiders with a sprained left foot although coach Dennis Allen said this one doesn't appear as serious.
"Obviously, it looks like Jacoby is going to miss a little bit of time, don't know exactly to what extent yet," Allen said. "We're still seeing where he's at."
Allen couldn't rule out the chance that Ford would miss the opener on Sept. 10 against San Diego.
The Raiders have only three receivers on the roster who have ever caught a pass in the NFL and all are nursing injuries. Darrius Heyward-Bey left the game Friday with a sprained shoulder that isn't believed to be serious. Denarius Moore hasn't played in the preseason as he recovers from a hamstring injury originally sustained during minicamp in June.
Allen said Moore is getting closer to returning but the team might need to look outside the organization for help at receiver.
Ford and Heyward-Bey weren't the only players to leave Friday night's game with an injury as Oakland dropped its second straight preseason game.
Backup quarterback Matt Leinart got stitches in his right index finger after being knocked out by an illegal hit by Ricky Lumpkin in the second half, and backup running Mike Goodson had weakness in his shoulder in his first game since being taken to the hospital with a neck injury earlier in training camp. Neither of those injuries appear to be serious.
There were some good signs in the game, especially from the first-team defense. Oakland continually pressured Arizona's quarterbacks in the first half for three sacks. The Raiders allowed just 52 total yards in the first two quarters, including only 11 on the Cardinals final five drives of the half.
Undrafted free agent Rod Streater had seven catches for 43 yards, giving him 13 receptions in two games. He also drew a pass interference call in the end zone and made a touchdown-saving tackle on an interception return.
But there were more negatives that will need to be fixed before the season opener.
The first-team offense failed to get into the end zone for the second straight game despite being in two goal-to-go situations in the first half.
"When we move the ball like we did, we need to get more points out of it," said quarterback Carson Palmer, who threw his second interception of the preseason and missed Darren McFadden on a potential touchdown. "We just need to keep our eye on the red zone and keep working on it."
Oakland had a punt blocked for a touchdown, missed an extra point, and allowed two long returns on special teams.
Goodson also fumbled twice, and backup cornerback DeMarcus Van Dyke allowed two long completions and missed a tackle on a touchdown run in the second half.
"We're a work in progress, offensively, defensively and special teams," Allen said. "I'm not real concerned about it. I know we'll get it corrected and work it to where we need to get to."
- LB Aaron Curry returned to the team after having his injured knee worked on in Los Angeles. Allen said he looked good running, and the team still needs to decide when to take him off the physically unable to perform list.
- TE Brandon Myers (shoulder) and RB Taiwan Jones (hamstring) could return to practice this week.