Pretty simple, really. Who will be the Rays' 5th starter on opening day? The Candidates:

Jeff Niemann:

Out of options, so he has to either be on the major league roster, traded, or put through waivers to Durham. The third option will positively lead to his going to another team for free, so that's not likely to happen. He was the Rays first round draft pick in 2004 and the 6'9" right hander has had two solid seasons following some injury troubles. Some want him as a bullpen arm where he could potentially throw high-90s.

David Price:

King David, number one overall draft pick in 2007. Price has electric stuff and between his fastball and slider, he could start right now. The problems are these: His change-up needs refining, leaving him in Durham could delay his arbitration years, and most importantly he has never thrown more than 130 innings in a season. It would be easier to control his innings in Durham and call him up to join the rotation sometime in May. Excellent golfer.

Jason Hamel:

Has been in the majors for the last couple of seasons, but was relegated to long reliever last year. His bendy things can be pretty nasty, but probably doesn't have the stuff to be a quality reliever. Could get some value in a trade, but isn't very valuable out of the Rays bullpen. Also out of options, so he has to either be on the major league roster, traded, or put through waivers to Durham.

Carlos Hernandez:

Used to be a top prospect in the Astros farm system before a partial tear of his rotator cuff threatened to end his career. Has had pretty good success since joining the Rays, but with the glut of pitching prospects he seems unlikely to make the roster on opening day. 

Others: Possibly Wade Davis or Mitch Talbot, but it's almost certainly going to be one of the pitchers described above.