The Vikings will be one of 23 NFL teams to start offseason workouts on April 17, the same day head coach Mike Zimmer is scheduled to undergo a fifth operation on his right eye.

Zimmer won't be missing much, anyway, since coaches aren't allowed on the field with players until two weeks into the NFL's offseason program. NFL rules limit team activity to weight lifting, conditioning and physical rehabilitation for the first two weeks of the voluntary workouts.

Beginning May 1, after the NFL Draft, the Vikings start on-field practices with limited team work. No live contact or team offense vs. team defense is permitted for the next three weeks.

Practices begin in earnest with the start of Organized Team Activities, during which full 11-on-11 drills are allowed without live contact for four weeks. Below is the Vikings OTA and mandatory minicamp schedule for this spring.

OTA #1: May 23-25

OTA #2: May 30-31, June 1

OTA #3: June 5-8

Mandatory minicamp: June 13-15

Zimmer, 60, said during NFL owners meetings last week that he'll have an oil bubble in his eye, used to hold a repaired retina in place, replaced April 17 with an oxygen bubble, which will prevent him from flying for two weeks.

The mid-April surgery had been scheduled so Zimmer could travel around the country this spring during the Vikings' draft preparations. Zimmer said he'll also undergo cataract surgery sometime in June.