Many of them will be pitchers, Black said.
"It's a luxury to have more pitchers added to take the burden off certain guys who have been here all year and with their workloads," Black said before Saturday's game against the D-backs.
But the Padres won't add players just for the sake of adding, Black said.
"There's something to keeping a roster that's useful and can function," he said. "It [number of players added] does vary from year to year, where you are in the standings, what you're trying to achieve with the players you're expanding with, and how you're going to use them."
There are a few no-brainers who will be added to the roster, like pitchers Robbie Erlin and Joe Wieland, who will likely get starts in September. Jesse Hahn, impressive during his rookie season, will rejoin the team as well.
Chances are pitcher Matt Wisler, the team's No. 2 prospect according to MLB.com, won't join the team. For starters, Wisler won't have to be protected on the 40-man roster this winter. He'll also set a career-high in innings and the team could be inclined to shut him down when Triple-A El Paso's season is done on Sept. 1.
Left-handed reliever Frank Garces, who was optioned to Double-A San Antonio Saturday when Andrew Cashner was reinstated from the disabled list, will be back.
The team could take a look at 23-year-old right-handed reliever R.J. Alvarez, who was obtained in July from the Angels in the Huston Street deal. Alvarez doesn't have to be protected on the 40-man roster this winter, but could be a part of the team's bullpen in 2015.
Alvarez has a 1.14 ERA in 34 games between two stops in the Double-A Texas League this season with 54 strikeouts in 39 1/3 innings.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.