Diakite was a regular under Paolo Di Canio, but Ball has preferred Carlos Cuellar in central defence so far.
And Cabral played in the opening game of the season but did not start again under Di Canio, and has not figured under Ball either.
Ball said: "There's no problem at all with Diakite or Cabral. It's not that they have been injured.
"It's just that I chose to go with the players I did for those games.
"People shouldn't read anything into it."
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