OWINGS MILLS, Md. -- The Baltimore Ravens were forced to cancel their Aug. 8 practice against the San Francisco 49ers at M&T Bank Stadium because of logistical issues, the team announced.

The collective bargaining agreement limits the number of consecutive days a team can practice or take part in football activities during training camp. The 49ers considered their travel day to Baltimore to be an "off day," but the players' union called it a work day, so Friday's open walkthrough had to be canceled.

"The way their schedule sets up, they're not going to be able to do it," coach John Harbaugh said. "It's not a big deal as far as practice. But it would've been neat for fans, and that's what is disappointing."

The Ravens and the 49ers will open up their preseason schedule on Thursday, Aug. 7 at M&T Bank Stadium. The teams will hold three joint practices (Aug. 9-11), but all will be at the Ravens' Owings Mills facility and closed to the general public.

The Ravens have an open practice at Navy Marine-Corps Stadium on Monday at 7 p.m.