Armstead (concussion) has been ruled out ahead of Monday's game against the Titans, C. Isaiah Smalls II of the Miami Herald reports.
Armstead entered concussion protocols during the Dolphins' Week 3 loss to the Seahawks. He wasn't able to practice in any capacity this week, and his next chance at playing will be Week 5 against the Patriots on Oct. 6. Kendall Lamm, who came in after Armstead left Sunday's game, will start at left tackle and be tasked with protecting the blindside of quarterback Tyler Huntley.