IRVING, Texas -- The Cowboys' signing of Derrick Dockery six days before the season opener was designed for games like Sunday’s against Detroit.

The Cowboys wanted to add bulk and height on the interior, which is why they cut Montrae Holland. Dockery weighs 325 pounds and is 6-6.

But a knee injury will keep Dockery out for at least another three weeks, according to a source. He suffered a tibial plateau fracture in his first start at San Francisco. With Dockery out, rookie Bill Nagy (6-3, 303) will start his third game and have to prepare for Lions defensive tackle Ndamukong Suh, perhaps the most powerful defensive tackle in the NFL.

And it won’t get easier for the interior linemen after the Oct. 9 bye either with a trip to New England and Vince Wilfork and (possibly) Albert Haynesworth at defensive tackle.