The Ravens got relatively good news Sunday on the health of rookie running back Kenneth Dixon, who was helped off the field Saturday, unable to put any weight on his left leg.An MRI taken Sunday revealed that Dixon has a torn MCL, which won't require surgery but could keep the former Louisiana Tech standout out for four to six weeks, according to a source.Dixon was hurt in the Ravens' 30-9 victory over the Detroit Lions when former Raven Haloti Ngata tackled him just outside the end zone. Dixon's left leg bent awkwardly on the play.The Ravens open the regular season in two weeks with a Sept. 11 matchup against the Buffalo Bills. If all goes well and there are no setbacks, Dixon could be ready to return by mid- to late September.ESPN first reported the results of Dixon's MRI.The Ravens have had four players — Justin Forsett, Buck Allen, Terrance West (Towson University, Northwestern High) and Dixon — work with the first team during the preseason, so they should have enough depth to withstand an injury without needing to sign another back.Dixon, however, leads the team with 107 rushing yards on 22 carries. He also had two receptions for 21 yards and was pushing for a more prominent role with his play in the preseason."It's the next man up," Forsett said after Saturday's game, in which the Ravens lost both Dixon and tight end Benjamin Watson (torn Achilles tendon). "We've been doing it for years. It's unfortunate those guys went down. They're special players, but things can happen and injuries happen. We've just got to keep pushing."