Abraham is attempting to come back from a knee sprain that has kept him out a month. He doesn't seem comfortable playing with the bulky knee brace he has been given to protect his LCL sprain. Also, he doesn't want to risk blowing out the knee entirely, and thus hurting himself in free agency this off-season.
Abraham's status could be negatively impacted by the inclement weather expected in San Diego Saturday night. Heavy rain is expected, and the field should be sloppy, especially since it rained all day Friday as well.
Chrebet, suffering from a mild concussion, was very limited in practice this week. Since he has a history of concussion problems, his chances of playing against the Chargers are slim.