Carolina Panthers running back DeShaun Foster was downgraded from questionable to doubtful with a knee injury for Sunday's game at Detroit. Meanwhile, starting running back Stephen Davis was upgraded from questionable to probable with his knee injury. Neither player practiced on Wednesday, but Davis returned to the field for both Thursday and Friday. Foster, on the other hand, has not practiced and it doesn't look like he will play on Sunday. Davis, who is coming off major offseason surgery on his right knee, also missed some practice time last week as well, but still took the bulk of the carries in Week 5's 24-20 win at Arizona. The team has been careful all season long with the 31-year-old, who ranks third in the NFL with seven rushing touchdowns this year and leads Carolina with 291 rushing yards. Foster has added 185 yards on the ground and is averaging 4.5 yards per rush as Davis' backup. He has also caught 12 passes for 188 yards.