Several players will be attending a minor league mini-camp beginning February 22 in Kissimmee. The roster for this portion of Spring Training has not been released. However, assuming the mini-camp involves only pitchers and catchers, which was the case in 2012, here's some speculation on who is going to Florida a little bit early.
A few weeks ago, The Grand Old Game posted a list of players who, according to his sources, had been invited to minor league spring training. His list included only pitchers and catchers. Working with this list and the Farmstros database, we find that the following pitchers and catchers aren't invited to minor league spring training and are likely candidates to be at mini-camp.
NOTE: On February 21, Brian McTaggart posted 20 players who are coming to mini-camp. 13 of the 20 were included below. The other seven are in Brian's post at the link above.