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ALAMEDA, Calif. -- Tyrone Wheatley's injury-plagued season took another turn for the worse Wednesday.

The Oakland Raiders running back will miss Sunday's home game against Kansas City with a torn left hamstring. He had an MRI on Monday and will likely miss two to three weeks.

He is not a candidate for injured reserve at this time, coach Norv Turner said Wednesday.

"If we needed a spot, he would certainly be a consideration," Turner said.

Wheatley, who missed three games in October with a shoulder injury and has also been nursing an existing foot problem, said after Sunday night's snowy 25-24 victory at Denver that he heard a pop in his leg after landing awkwardly late in the third quarter.

Wheatley caught a pass in the open field and Denver cornerback Kelly Herndon's shoulder pads jarred into Wheatley's right knee and caused him to land hard on his left leg. Wheatley grabbed the back of his thigh in pain and was quickly carted off on a tractor with a snowplow on the front.

Turner said Monday that Wheatley was questionable this week and seemingly downplayed the injury, saying, "We were probably lucky there."

"They did the MRI and you know how that is. Guys feel good about it and you talk to them, then the MRI tells the truth," Turner said.

Wheatley has 85 carries for 327 yards and four touchdowns this season for the Raiders, who are averaging a league-worst 75.4 yards rushing per game.

"Tyrone is a big physical presence back there, but there are other guys who add things, too," quarterback Kerry Collins said Wednesday. "It's kind of been running back by committee and Tyrone has solidified that a little bit. If he's out, other guys are going to have to step up, and I think they will."

That means Oakland (4-7) will be counting on more from Amos Zereoue.

"I wish I could sit here and say I'm going to run for 100 yards," Zereoue said.

To improve their depth in the running game, the Raiders signed fullback Chris Hetherington on Wednesday and released linebacker Maugaula Tuitele.

Hetherington, cut by the Raiders in September, appeared last year 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. He could play on special teams and at fullback Sunday.

"I've been cheering for them, but I haven't been watching," he said. "I just want to come in and help out any way I can."

Copyright 2004 by The Associated Press