The OKC-Houston game was a very clear example of the difference between regular season basketball and playoff basketball.
Teams pick out matchups and exploit them over... and over... and over again on both sides of the court. On defense, Houston completely disrespected Dort, ignoring him entirely in favor of playing 5-on-4 on the other OKC players. That worked... Dort kept chucking up shots that he can't hit. And on the other end, Harden continually exploited SGA. That also worked. Harden shot 11-15 from the field, much of it at SGA's expense.
OKC will have to come up with some counters if they want to force a game 7.