I don't really like playing the "when Tatum comes back" hypothetical games, it feels a little presumptive, with a chance to cause a jinx. But what I will say is that when Walsh started to play more with the starters, I was worried that having both Walsh and Queta on the floor would not be enough offense. For a while, Walsh was hitting everything in sight so he was proving me wrong in a big way.
Then he had his illness and missed some games and has hardly played since. So to me, it depends on which version of Walsh it is. If he can be that 3&D guy, I want him in the line up. I always prefer tall ball to small ball. But if he is not that guy, then he shouldn't start. I don't see this as being about Tatum. I actually prefer Pritchard off the bench, in any case.