Arnold, who left Monday's practice with a pectoral injury, is expected to be available for the Lions' regular-season opener against the Rams on Sept. 8, Ian Rapoport of NFL Network reports.
Arnold has picked up a couple of injuries during training camp, and while none have resulted in a long-term absence, it appears he'll be held out for the Lions' final two preseason games. The rookie first-rounder is expected to start at outside corner opposite seven-year veteran Carlton Davis. Arnold will get his first taste of NFL action against veteran quarterback Matthew Stafford and All-Pro wideouts Cooper Kupp and Puka Nacua in Week 1.