Howard suffered the injury when England striker Emile Heskey slid into him during the first half of the 1-1 draw in Rustenburg on Saturday but carried on after receiving treatment.
"At this point, there is no answer," Bradley told reporters on Sunday when asked if Howard was doubtful for Friday's match in Johannesburg.
"When you see the way Timmy handled himself after the collision, you'd certainly expect he will be on the field again."
"He'll be evaluated later today and then a decision will be made whether he will need further tests. Obviously he was sore, he did a great job of taking a tough hit, staying in it and playing it really well. We will assess it and figure out how to go on from there."
The States have Marcus Hahnemann and Brad Guzan available as back-up.
Bradley said that after a tough encounter with England, he expected Friday's opponent's Slovenia to offer another style.
"I think it will be a different kind of game, obviously we will watch them but they are a hard working team, well organised and they have an ability to sometimes sit back a little and still catch you on the counter.
"Overall, the pure speed and physicality of Saturday's game is on the very high end and the Slovenia game, in some ways, might be a little more of a chess match," he said.
