Dallas Cowboys tight end Jason Witten has been diagnosed with a lacerated spleen and could miss the rest of the preseason.

Witten was hurt during the first quarter of Dallas' preseason opener against Oakland on Monday after taking a hit from Raiders linebacker Rolando McClain.

"It's a very serious injury and we're really taking this day-by-day," Cowboys coach Jason Garrett said. "He has to be very still and idle for the next week to 10 days. You won't see him out on the practice field. We have to make sure he heals as well as possible and as quickly as possible."

Garrett said that Witten won't play in both Saturday's game versus the San Diego Chargers and the next week's game against the St. Louis Rams.

The seven-time Pro Bowl selection has been extremely durable during his nine- year career in Dallas, missing just one game during his rookie season in 2003 when he suffered a broken jaw.

Witten has caught 696 passes for 7,909 yards and 41 touchdowns over 143 games, all but 10 of which have been starts, with the Cowboys.