Nope. Simmons has elite ball skills. Poythress has never been a very solid man defender. Poythress is an elite rebounder though. But so far, Poythress isn't even starting. It generally takes more than a year to get back to 100% after an ACL.
I've always thought Poythress was a pretty good defender. It's obvious the kid aint at 100% yet and he may not be at any point this year, but if he does, he will do a decent job on Simmons. No one guy is going to stop this kid. Simmons has talent and is for real, but basketball is a team game and one guy won't beat you. He will get his, but Poythress at 100% would do the best job of any forward in the country guarding this kid imo.