IRVING, Texas -- The Dallas Cowboys won't have their complete backfield Sunday after all.
"We're trying to get to the bottom of what it is," Garrett said. "He's been sick all week long and we're just kind of monitoring those symptoms and we're going to continue to do that to see what the origin is."
Jones went through his third straight day of limited practice and is listed as questionable on the injury report, but he is expected to play. What Jones' role will be, however, is not clear. DeMarco Murray has rushed for 601 yards in Jones' absence and the rookie running back will continue to be the starter.
Jones, who ran for 253 yards on 63 carries and caught 14 passes for 105 yards in the first four games, could be the third-down running back and also return kicks. He handled kick returns with a group of players in practice this week and averaged 24.2 yards a return in 2008-09.
Fiammetta, who was claimed off waivers from the Carolina Panthers in September, has played a key role in the recent success of the Cowboys' running game. He does not have any rushing yards this season, but Fiammetta has been a force as a lead blocker, prompting owner/general manager Jerry Jones to call him the franchise's best true fullback since Daryl "Moose" Johnston.
In the six games Fiammetta has played this season, the Cowboys have averaged 145.8 rushing yards and 6.6 yards per carry. They averaged 84.6 rushing yards and 2.5 per carry in the three games Fiammetta did not play. The vast majority of rookie Murray's franchise-record 601 yards in the past four games have occurred with the 6-foot, 242-pound Fiammetta on the field.
"What I know is that it reaffirms how important a fullback is to what we're trying to do offensively, what Jason wants offensively," Jones said after last week's blowout win over the Buffalo Bills. "This fullback is a big incremental thing. I've always known that, but there's no substitute for a prototype fullback relative to trying to do it with tight ends. It just works better."
Garrett said the Cowboys are considering promoting rookie fullback Shaun Chapas, a seventh-round pick from Georgia, from the practice squad. Tight end John Phillips has played fullback when Fiammetta was inactive.
The Cowboys will be without two offensive starters against the Redskins. Pro Bowl receiver Miles Austin will miss his second consecutive game with a strained hamstring.
Cornerback Mike Jenkins is also out with a hamstring injury.
Quarterback Tony Romo also will continue to be the holder on field-goal and PAT attempts.
Right guard Kyle Kosier is also questionable but has not missed a game this year.
Linebacker Sean Lee will play for the second straight game with a cast protecting his dislocated left wrist, as will punter Mat McBriar, who has a nerve problem in his left leg. They are listed as probable.
Tim MacMahon covers the Cowboys for ESPNDallas.com. Information from ESPNDallas.com's Todd Archer was used in this report.