Wheatley, who missed three games in October with a shoulder injury and has also been nursing an existing foot problem, injured the hamstring in Sunday night's 25-24 win on a snowy night at Denver.
After catching a pass, Denver cornerback Kelly Herndon tackled Wheatley in the open field. Herndon's shoulder pads jarred into Wheatley's right knee and caused him to land hard on his left leg.
Wheatley has 85 carries for 327 yards and four touchdowns this season. The Raiders have the NFL's least productive running game but Wheatley is the closest thing to a consistent threat.
That means Oakland (4-7) will be counting on more from Amos Zereoue, who filled in for Wheatley when he was injured.
The Raiders released Hetherington last season appeared before a grand jury investigating a nutritional supplements lab -- the Bay Area Laboratory Co-Operative -- which has been at the center of a steroids controversy in several sports.
Since being cut, Hetherington has been home in Arizona working out and playing golf, waiting for a team to call.