Lions' Darius Slay challenging Raiders' Derek Carr with 'sticky' coverage

Lions-Raiders joint practice, Aug. 7(Photo: Daniel Mears, Detroit News)Napa, Calif. -- Joint practices have offered some stiff challenges for Detroit Lions cornerback Darius Slay. Two years ago, he went head-to-head with Pittsburgh's Antonio Brown, arguably the game's most-compete receiver. And last year, Slay was asked to hang with speed merchant T.Y. Hilton.

This offseason, the early-camp test is about physicality and size, with Slay spending most of two practice days lined up across from Raiders wideout Amari Cooper.

"He's bigger, size-wise, with the muscles, than I thought, from the last time I seen him," Slay said.

The All-Pro cornerback isn't wrong. The 6-foot-1 Cooper reportedly bulked…