The Indians are one of the biggest surprises of the 2011 season, going 13-6 after losing over 90 games each of the last two seasons. Both their hitting and pitching are much improved, but the hitting seems especially likely to fall a bit. Last year, they were ranked 26th in runs scored, and this year they're 3rd.
The ranking might be a little high because they've played 19 games while other teams have played less (Yankees at #8 have only played 16 and have scored 11 fewer runs), but their offense is doing very well even taking that into account.
They've gotten a boost from the return of Grady Sizemore who made his season debut (he had been on the DL) just last week and is hitting over .400. They have some quality hitters (especially Shin-Soo Choo), but you have to wonder how long a lineup with Carlos Santana (.215, 2 HR, 10 RBI) hitting cleanup can remain at the top. The bottom of their lineup is unimposing (Matt Laporta, Adam Everett, Michael Brantley, Jack Hannahan).
That is going to end up putting a lot of pressure on Travis Hafner to produce at a high level (which is fair since he's making $13 million this year). If he hits like the perennial MVP candidate of 2004-2006, the Indians might have no trouble scoring enough runs. If he hits gets hurt and struggles like he did from 2007-2010, then it's hard to see them having enough firepower to compete unless they have lights-out pitching all year.
If Sizemore and Hafner hit like it's 2006, the rest of the lineup can be decent complementary players and they can win. If they get hurt or struggle, the rest of the lineup is almost certain have difficulty scoring enough runs to remain competitive.