Vikings: Shamar Stephen, Carter Bykowski have surgery

EDEN PRAIRIE, Minn. -- The Minnesota Vikings will likely be without defensive tackle Shamar Stephen for the rest of the preseason after the second-year player had arthroscopic surgery on his knee. Coach Mike Zimmer said on Wednesday, however, that the Vikings expect Stephen back by the start of the regular season.

The former seventh-round pick played 414 snaps for the Vikings as a rookie, becoming a regular piece of the team's defensive tackle rotation last season and starting three games. His absence means the Vikings will have more playing time for backups such as B.J. Dubose and Leon Mackey at the end of the preseason, but Zimmer didn't seem worried about Stephen's long-term availability.

Zimmer said tackle Carter Bykowski had surgery on his shoulder and wasn't sure when he would be back.

Safety Antone Exum, who hasn't practiced this week, is dealing with a hamstring issue, Zimmer said, and center John Sullivan missed practice with "spasms," though Zimmer didn't specify whether it was his back or somewhere else.