Oakland Raiders running back Latavius Murray failed to pass the final test of the NFL-mandated concussion protocol and will not play Sunday against St. Louis.

Murray had been limited in two practices earlier this week but was held out of Friday's workout after being ruled out against the Rams.

Interim coach Tony Sparano declined to go into details about Murray's situation or whether the second-year running back had suffered any type of setback.

Losing Murray is a significant blow to Oakland's offense.

He rushed for 112 yards and two touchdowns in the Raiders' 24-20 win over Kansas City on Nov. 20 — the team's first victory in more than a full calendar year. Murray was knocked out of the game in the first half after absorbing a helmet-to-helmet hit by Chiefs' safety Kurt Coleman.