It wasn't really the fault of either. The two were both going for a pass intended for DeSean Jackson when they collided mid-air and landed hard. A few reporters on the scene noted that the hitting the ground seemed to be the biggest knock Nnamdi took. Both guys were down, but Nate Allen got up fairly quickly and has since returned to practice.
Asomugha, on the other hand, stayed down for several minutes before getting up, being helped to the cart and taken to the locker room. When we get an update on him we'll pass it along. Several reporters at camp today described Nnamdi as being "knocked out."
[Update by JasonB, 08/13/12 5:14 PM EDT ] Eagles say Nnamdi has a lacerated lip and a sore neck. He is also undergoing the concussion tests that are protocol in this situation. Asomugha did suffer a concussion last year in the week 13 game against Seattle.
Also, speaking to reporters after practice, Nate Allen said that Nnamdi was talking while on the ground, which would refute the reports that he had been "knocked out." Allen says that Asomugh's helmet his chest.