Tonali is returning to full match fitness after missing almost the entire last season due to a betting ban.
Ahead of Saturday's clash with Arsenal, Howe was asked about the Italian's role: "All options are open. Sandro can definitely play both positions, whether it be higher or lower, and that's why we recruited him in a way, because he had that versatility. We didn't want to sign one player for one position. We needed that flexibility, especially going into a Champions League season that we faced.
"I think Bruno (Guimaraes) is slightly more complex in terms of where he plays, because I think he has natural strengths, where he gravitates to the ball and always wants to be on the ball, and that's his biggest strength. Playing him away from the ball is different for him, so that's something we will look at. I think good players can play anywhere, so let's see."
On squad depth, Howe says he's satisfied: "They certainly give you the ability to change the team. Many times I've said I don't want the team to pick itself, but I also don't want to go game to game, changing too many players, because I don't think that's healthy either.
"So I believe in a settled team, but of course, with midweek fixtures especially, the intensity of games now, you have to have the ability to rotate. I'll pick the strongest team that I can, that can give us the best chance to win."