Tuesday's USC football practice was barely notable on the field. The quarterback competition continued cautiously, without any clue as to who will start next Thursday at Hawaii and no man on either side of the ball made any memorable or outstanding plays. 

In a word, the last fall camp practice on Howard Jones Field was all about absence: an absence of story lines, but most importantly an absence of players.

Head coach Lane Kiffin said he was "concerned" about the lack of participation from his worn-down and injured players. He estimated that at least 21 players did not even practice Tuesday - and that's not even counting the number of athletes, mostly starters, who wore no-contact pinnies. 

"We went backwards," Kiffin admitted. "We've got some really short lines and unfamiliar faces, which is very concerning. But we're physical."

Surely when 21 players don't practice on a single day, that may be attributed to the intensity and length of the camp, which has not ceased for 18 straight days - and 22 practices. Wednesday's scrimmage at the Coliseum will mark the final official practice of fall camp before a much needed day off on Thursday. The Trojans will begin their preparations this coming Friday for their first game against Hawaii.

Among the players that did not practice today were defensive backs Su'a Cravens, Gerald Bowman and Dion Bailey, offensive lineman Aundrey Walker, running back D.J. Morgan and tight ends Randall Telfer, Xavier Grimble and Jalen Cope-Fitzpatrick. 

With the Trojan's top three tight ends out with injury, there is a credible cause of concern.

But Kiffin mused on his healthy tight ends, "One (Chris Wilson) was a quarterback a week ago, one (Shane Sullivan) we're just learning his name and the other one (Kevin Greene) was a defensive end a week ago. They're doing the best they can."

SEE MORE: USC Football Fall Camp, Day 17: Final Two-A-Days As Opener Looms

To add injury to injury, there were several Trojans who still could not make contact in 11-on-11 drills, many of which were starters. They included wideouts Marqise Lee and Darreus Rogers, linebacker Hayes Pullard and running backs Justin Davis, Tre Madden and Silas Redd. 

For the first time all camp, Kiffin expressed severe doubt about Redd's ability to play next Thursday night.

"Silas is not really back," he claimed. "We're pushing him slow out here until he's fully healthy. I'm not sure that he will be [ready], but I hope so."

With the starting running back, cornerback, tight end and - oh yeah - quarterback positions all still in question due to inconvenient injury and consistent competition, tomorrow's organizational scrimmage has become all too important for the Trojan coaching staff to judge the uninjured talent left on the field, with just eight days remaining until Honolulu.