The Titans also placed first-round draft pick Jeffery Simmons on the non-football injury list. Simmons, a defensive tackle from Mississippi State, tore the anterior cruciate ligament in his left knee in February.
Casey, a four-time Pro Bowl selection, missed the Titans' final game last season due to an injured left knee. Smith had 20 catches for 258 yards and three touchdowns in 13 games last year before a knee problem caused him to go on injured reserve.
They will be eligible to practice with the Titans after passing a physical.
Titans rookies, quarterbacks and players recovering from injury reported to training camp Monday. The remaining players report Thursday.
The Titans open training camp Friday.