The Pirates tweet that they have added catchers Tony Sanchez and Ramon Cabrera and pitchers Phil Irwin, Victor Black and Hunter Strickland to their 40-man roster, protecting them from the Rule 5 Draft.
Assuming shortstop Gift Ngoepe is ineligible (and that was unclear, although he probably isn't), the only notable player who was left off the roster was pitcher Kyle Kaminska, who came over in the Gaby Sanchez trade and had a good showing in the Arizona Fall League. That the Pirates didn't add him may indicate that they don't think highly of his stuff. The most surprising player to be placed on the roster was Hunter Strickland, who's a big pitcher who hasn't put up impressive numbers.
Sanchez will likely make his big-league debut next year, whether or not the Pirates acquire a new catcher this offseason to pair with Michael McKenry. Cabrera is a little bit further off and is unusually small, and he posted mediocre numbers at Altoona this year, but he was only 22 and has hit for good averages in the past.
Irwin, a righty, has posted strong numbers throughout the minors despite underwhelming stuff. Black struck out 85 batters in 60 innings for Altoona this year and could eventually be a late-inning reliever, although relief prospects are a dicey bunch.