The Hammers have made nine signings during the summer transfer window, leaving Pellegrini with more than 25 players available to him in the coming months.
West Ham could still loan out fringe members of the group before the end of August, but Pellegrini has indicated that he is happy to have a number of options in each position.
At a press conference, the Chilean told reporters: "For me, as a manager, the difficult thing is when you don't have options. When you have different options, I have to chose the starting XI but also they know that if during the whole season if you don't have a strong squad, it is difficult to be successful.
"We have players in two different positions and they must work in a competitive way between them. Then I make the decisions, options wise, on who plays."
West Ham begin the new campaign away at Liverpool on Sunday afternoon.