In terms of who the 5 man rotation will be I think it could be a pissing contest in here until we are in week two of the season. The first three are locks in Sale, Porcello and Price but after that there is a good argument for all of Wright, Pomeranz, and ERod.
Drew Pomeranz.
Why he will be the starter: Because of his first half last year, the hefty price the Sox paid for him, and the hope that with some added stamina he can replicate his first half for a whole season going forward.
Why he won't be the starter: Someone is the odd man out, he doesn't have the ability to lock down a rotation spot for 32 games and he has more experience of pitching out of the bullpen than the other three. With sucess I might add.
Stephen Wright
Why he will be the starter: Again he had a really good start to the 2016 season, and at the end of the day he really only had one bad 6 week stretch in August and September. Besides that he pitched like an ACE most of the year and has a track record of average to above average results in Boston and the minors the past 3 years.
Why he won't be the starter: No matter how well knuckleballers pitch they always seem to come with some question marks. Their performance can be volatile from game to game and from season to season. There is a sense he was pitching above his talent last year and again at the end of the day someone has to be the odd man out. For a guy who is kind of a one trick pony it becomes pretty easy to throw him into the swing man role which also allows the Red Sox to avoid optioning Eduardo Rodriguez.
Eduardo Rodriguez
Why he will be the starter: Talent and upside. We've all seen his potential here and in Pawtucket the past few years, with youth on his side and injury behind him he seems primed for a break out season. He very well may have the capacity to be the better pitcher over the next few years than Wright or Pomeranz.
Why he won't be the starter: He has an option left, which gives the Sox the option to keep him ready in Pawtucket if anyone from the five man rotation goes down or severely under performs. History tells us this will happen. Despite his upside and high ceiling talent he's never seemed to fully put it together for a full season and considering the last point I made it makes sense for him to get some innings in Pawtucket and prove he's ready and overcome some of his pitch tipping issues while he waits for his next chance.
Now I'm sure some here would agree or disagree with many of these points but that's they whole point of this post. I don't think there is a silver bullet answer for what to do, but if I had to guess I'd say all things being equal in spring training that Pomeranz and E-Rod take the 4th and 5th spots while Wright becomes the swing man out of the bullpen. But as the old saying goes, these types of things have a way of working themselves out.