Howard's non-guaranteed deal with the Spurs was only confirmed on Friday and he has now expected to play for their D-League affiliate the Austin Toros.
"He's just trying to get in shape and see what his body feels like and see if he can play at a level that would be advantageous for him for another team he could go to," San Antonio coach Gregg Popovich revealed to reporters.
"I think he's making a great effort to establish that and not worry about how things look, but just trying to get back in the game.
"I think it shows good character on his part to do that and not worry about what people are thinking."
The Spurs begin their season against the Memphis Grizzlies on Thursday.