Bills RB Karlos Williams diagnosed with concussion

— -- Buffalo Bills running back Karlos Williams suffered a concussion Sunday and is considered day-to-day heading into Week 5 against the Tennessee Titans, general manager Doug Whaley told WGR 550 SportsRadio on Tuesday.

Williams, a fifth-round rookie out of Florida State, filled in for injured  LeSean McCoy and rushed 18 times for 40 yards and caught a 23-yard touchdown pass during the Bills' 24-10 loss to the New York Giants. McCoy remains out with a hamstring injury.

Williams now enters the NFL-mandated concussion protocol and must be cleared before returning to physical activity.

"He told our trainers several hours after the game that he wasn't feeling well and our medical staff took a look at him," Whaley told WGR 550. "They put him through further evaluations late yesterday afternoon and it was determined that he'll have a concussion. So we'll see how he proceeds throughout the week."

If Williams and McCoy cannot play Sunday against the Titans, the Bills would turn to Boobie Dixon and Cierre Wood at running back. Whaley told WGR 550 that the Bills could sign another running back this week, and said it was "a possibility" that the Bills could target Bryce Brown, who was released by Buffalo last month.

Running backs Trent Richardson and Alfonso Smith were among the free agents the Bills worked out at their facility Tuesday, according to multiple reports. Richardson, the third overall pick in 2012, has been a bust after his rookie season, and was most recently dropped by the Oakland Raiders.

"We'll see if we can add some guys to help us depth-wise, but we have full confidence in the guys we have," Whaley said. "We feel very comfortable with Boobie Dixon and Cierre Wood, that they've been here.

"Again, Karlos, with that concussion protocol, he may be able to -- you know, day to day -- and hopefully he'll be in there at the end of the week."

Williams gained 110 yards on 12 carries in a Week 3 win over the Miami Dolphins.

McCoy told reporters last week that he won't play until he feels 100 percent after suffering a setback two weeks ago in his recovery from a hamstring injury.