Gibson, who has been working with Oakland's starting defense, became the latest member of the Raiders stricken by sickness. Defensive back Stanford Routt, tight end Marcellus Rivers both missed practice earlier this week because of strep throat. Both were back on the field Friday.
The two join a growing list of Oakland players sidelined. Running back LaMont Jordan remained absent from practice while nursing a sore quadriceps muscle, wide receiver Carlos Francis is out with a hamstring injury and tackle Robert Gallery (quad) has yet to participate in a training camp practice.
''There's a bug going around,'' head coach Art Shell said. ''I had (trainer Rod Martin) speak to the team last night. For whatever reason we've had about five guys come up with high fevers, some kind of bug. So we're trying to make sure, with your sanitary things, you have to take care of them.''
First-round pick Michael Huff replaced Gibson in the starting lineup and took his first reps with the first-team unit.
Jordan's injury, incurred during a Thursday scrimmage, prevented him from practicing and opened the door for back-up Justin Fargas to get reps with the first team offense. Fargas ran well for the most part, and had a hand in the first dust-up of camp. He and linebacker got into it during the morning practice after Clark gave the running back an extra shove. Fargas, who has been injured for the better part of the last two seasons, turned and threw the ball at Clark's head.
Nothing further came of the incident.
''You go three or four days and guys start getting irritable and the least little thing can set somebody off,'' Shell said. ''So there's nothing to panic about, that's part of the deal. Fighting ... wasted energy.''
* Former Raider and current Executive Director of the Players Association, Gene Upshaw, was on hand for watch both practices. After the afternoon session ended, Upshaw and Shell joined ex-teammates Willie Brown and George Atkinson for a 15-minute meeting that ended with all four chuckling. ''Just sharing old war stories,'' Shell said.
* Veteran cornerback Tyrone Poole had the day's biggest play when he blitzed and knocked the ball out of quarterback Aaron Brooks' hand. Poole then scooped up the loose ball and returned it 30 yards before being pushed out of bounds.
* Oakland's first-team offense struggled on three straight plays during a hurry-up drill, and then, to make matters worse, kicker Sebastian Janikowski shanked a 52-yard field goal attempt.