Here are my choices on who to protect:
Lock: J. Quero. Absolute no brainer
Maybe (AAA) - Devanney, N. Campbell - 2nd year I have been pushing Cam. He's deserving, as well as Campbell, The Brewers have not shown to protect utility type guys like this so its probably unlikely, but I'll keep listing Cam every year.
Maybe (AA) - Zamora - Has had a great bounceback from last year. I think he is next likely to be protected, especially if promoted to AAA this year (and performs well).
Maybe (A+) - Bradley Blalock, Edwin Jimenez, Alexander Cornielle - All three are long shots but if they got promoted to AA this year, the likelihood goes up. Cornielle is really a long shot, but I'm a big fan. He had a bad May, but has pitched much better the last two months. Both Jimenez and Cornielle are young for the league and are holding their own. Would hate to lose either. Blalock is a year older but is likely to see AA soon. His numbers are better and is more likely to be protected of the three.
I'm considering McKendry just because he is new, but I think he is unlikely. Not listed as a ranked prospect in any TB lists I could find, he is probably safe from being drafted. Isaac Collins certainly has the numbers to justify being protected. I'll reserve judgment until I see how he does in AAA. He's a bit old for AA, so want to see him perform at the next level first.
In summary, its quite likely Quero is the only one they protect. However, they have plenty of 40 man roster space so you may see a couple of these guys may get protected. We have a couple of months yet to evaluate so things are still likely to change.