...with ease

There's no way in hell that Wales will beat us. They weren't even supposed to be there.
We're going to smash them, just like we did all the other teams
-with the exception of NZ in the pool stages. But don't worry their "smashing" will come in the final
Anyway, this puts some stuff into a little more perspective:
SA Rugby Mag has always been critical. Gatland alluded to the French being the better team on the day and that the red card gave them the means to win the match. He approached the Q&A with honesty, even Rassie does that.
I still believe we have the better, or even the best, pack in the RWC.
Wales have been up and down in this competition and they had to trade on replacement players digging into their depth and continuity which impacted the rate at which they play at. They may pretty much be on the up against the Springboks.
It will be a good game to watch.
Just remember that England, France and New Zealand had a week extra to rest. The Springboks had the longest scheduled rest between the pool and knockout phase, but this wouldn't have had any impact on the Japan vs Springbok match schedule in any case. France simply had more time to prepare against Wales.