ALAMEDA -- Raiders rookie tackle Menelik Watson will miss up to a month after having arthroscopic knee surgery, ESPN's Adam Schefter reported in a tweet Thursday.
Watson missed almost all of training camp with a calf injury sustained during training in the offseason. After one padded practice, Watson was inserted at left tackle and played into the third quarter of the preseason finale against Seattle, playing well enough to earn the starting job.
He never made it to the opener, injuring his knee. Raiders coach Dennis Allen has been asked about Watson's condition and declined to give specifics regarding how long Watson will be out.
Asked if he had any information on Watson Wednesday, Allen said, ``Nothing other than he didn't practice today.''
The Raiders added tackle James Cornell to the practice squad to replace Matt McCants, who was elevated to the 53-man roster when it was determined Watson would not play against Indianapolis.
There was no sign of either Watson or tigh tend David Ausberry (shoulder).