I wouldn't pencil in Pizarro in the starting lineup just yet. He has to acclamated with his new teammates. Of course, theres still a very underrated Hugo Almeida too.
Martin Harnik is more of a forward than a midfielder but his natural position is that of a forward-winger which doesn't exist in Bremen - though Schaaf tried it in the preseason a few times with Martin on the right and Hunt or Husejinovic on the left wing. It's always hard to predict but I think Rosenberg is the #1 forward at the moment. Pizarro will have the advantage of being new. I think both Sanogo and Almeida are very close to those 2 though. I think Harnik will get playing time as well because of his versatility. He's also able to play right fullback.