With the news that Zach Miner has been been essentially ruled out as the fifth starter to open the season, the field has been narrowed to three candidates. The three are Nate Robertson, Rick Porcello and Dontrelle Willis, although it's hard to imagine Willis opening the season in the rotation the way he has pitched.
After two scoreless outings (seven innings total), Robertson is probably the front runner at the moment. His ERA for the spring is now down to 3.27 and recent reports on him have been good - he's working both sides of the plate with improved control and his slider has been sliding again.
Rick Porcello has been impressive all spring and I do not think they would be afraid to insert him into the rotation in April if there were no other options. However, ideally he would start at Erie to get a little more work and to delay his service time clock. If none of the veterans were to show they were ready, then Porcello would be the number five starter. That's the way it looked about a week ago. If Robertson continues to pitch well though , then I think that is the direction they will go.
Regardless of all the positive stories about how Dontrelle Willis is making strides this spring, he has had no good outings and his control is still a major problem - seven walks and two hit batsmen in 8 2/3 innings. I suspect he will be asked to start the season in the minors. He doesn't have to accept such an assignment but, if he were to refuse, he would forfeit two years of salary. Since nobody else is likely to want him on their Major League roster right now, I don't think he'd have any choice but to accept.