Allen, who has been dealing with a hamstring injury, left Thursday's practice with a trainer, Jeff Miller of the Los Angeles Times reports.

Allen, who has missed two straight games, logged a limited practice Wednesday, but his exit from Thursday's session is a situation to monitor ahead of Sunday's game against the Texans. If Allen is unable to return to action this weekend, Joshua Palmer and DeAndre Carter would continue to see added WR opportunities for the Chargers in Week 4.