Vikings' rookie RB Adrian Peterson is nobody's sleeper. On average, he was selected 50th overall. What was not expected was his Week One performance of 103 rushing yards and a 60-yard TD reception following a first half injury to starting RB Chester Taylor. As a result, many fantasy teams are forced into deciding who to start this weekend - the RB2 they drafted prior to taking Peterson or Peterson himself?
What I would do is ask myself, "If Adrian Peterson was the starter from Day One, where would he have been selected?" How one answers this conjecture leads one towards the decision to sit your RB2 and start Peterson. If you believe Peterson would have been a top second round/late first round pick, a simple solution is to start him ahead of your current RB2 if that RB2 was selected later than that. The major issue then becomes the fear every fantasy owner has about the good player you chose to bench - he goes off while Peterson flails.
That is the simpler solution. The decision becomes much tougher if you selected late in the first round and took two RBs very close to each other i.e selecting 10th in a 10-team league. In a situation like this, you have likely taken Willie Parker and Laurence Maroney (ADPs of 8 and 11) or Rudi Johnson and Reggie Bush (ADPs of 9 and 10). Now you must decide which RB is worse than Peterson. Is it Maroney? Is it Bush?
In this case, the fear of sitting the wrong back is very real. Will Maroney be able to effectively run against a San Diego defense? Will Sammie Morris get 8-10 carries? If you answer no and yes, then starting Peterson is easier to do, but will Peterson get all the touches like he did last week following Taylor's injury or will Taylor play and grab 10-12 carries to hurt Peterson's potential?
Or will Reggie Bush be able to shred the Tampa Bay defense rushing and receiving and break a big score - the exact reason you took him so high? Do you believe he is due this week after being shutdown last week against the Colts? Can you risk missing that by starting Peterson?
In this case, you choose Peterson only if you would have taken him ahead of Maroney or Bush and live with the consequences. Personally, I'd start Peterson over Bush because I'd never have selected Bush before any RB who has the lead rushing job and over Maroney because I'd have looked at Chester Taylor's 2006 workload and concluded Peterson would get as much work as the starting back.