ESPN's Adam Schefter reported Tuesday that the cornerback out of Mississippi State underwent arthroscopic knee surgery last Friday. The procedure comes as a surprise, but Slay is expected to be ready "well before training camp," according to Schefter.
Slay told Around The League before the 2013 NFL Draft that doctors said surgery would not be required on the torn meniscus he suffered in his right knee during the offseason. ESPN reported last month that a pocket of opposing physicians believed that a procedure ultimately would benefit the defensive back.
Slay produced strong results at the NFL Scouting Combine and went into the 2013 NFL Draft at No. 59 on Mike Mayock's Top 100 big board. The Lions -- who didn't expect the injury to be a major concern -- already have penciled in Slay as their starting right corner. They hope he can bring more to the Lions out of the gate than recent second-rounders Titus Young and Mikel Leshoure.
Follow Marc Sessler on Twitter @MarcSesslerNFL.