Love this question. TP to the OP.
Because today's NBA is so pick and roll oriented, and teams get caught in switches on defense almost every possession, I'm not sure it matters to have that one guy who can guard a particular superstar. You need multiple guys to throw at players like James and Durant. And that's what we have. You could make the argument that you've got four of those guys, even with Hayward down: Brown, Tatum, Ojeleye, Morris.
Think of this: If you're closing lineup is Irving/Smart/Brown/Tatum/Horford (or replace Morris for Tatum or Smart), then basically four out of the five players on the floor are either good wing defenders, or at least hold their own for a few seconds without getting abused.
That's what makes this defense so potentially deadly. It's not about one guy. It's about waves of guys.