Currently, Mendenhall has 136 carries for 517 yds for an average 3.8 ypc and 6 TD's on the season. Not exactly stellar numbers to say the least but still plenty of time for him to reach the 1000 yds rushing goal for the season; atleast in theory. His best game so far this season was the 146 yd effort against the Jaguars. His next best game rushing was 70 yds against the Patriots. The rest of the games he's coming out with yardage no higher than 66 yards rushing.
The next closest on the team is of course Isaac Redman with 64 carriers for 245 yds. A 3.8 ypc average and 1 TD, so we know he's not going to get there.
Right now Mendenhall is slightly below his average for the entire season, per rush, when he finished with 3.9 ypc last year. In 2010 though he did finish with 1,273 yds and 13 TD's. The Steelers schedule does lend itself to good running performances the rest of the way (except for maybe the 49ers game) should they choose to go that route but something tells me that we'll be seeing a lot more Ben and the passing game and Mendenhall could be hard pressed to reach that 1000 yds on the season.