This is from NFL.com today:

The Pittsburgh Tribune-Review reported Wednesday that the Steelers are hoping to have Bell return in a month. This is not a surprise. NFL Media Insider Ian Rapoport reported in late August that Bell would likely miss around six weeks with a Lisfranc sprain in his foot.

Tomlin disputed the Lisfranc diagnosis publicly at first, but the Tribune-Review confirms Rapoport's original report on the issue. (Tomlin did not address Bell's situation on Tuesday.) Rapoport checked in on the situation on Wednesday and nothing has changed. Bell is only jogging at this stage, NFL Media's Aditi Kinkhabwala noted a few days ago.