With the roof closed on Rod Laver Arena because of heavy local rain, and the subsequent high humidity in the building, the ball was heavy and flat, helping Nadal keep the ball in play.
Nearly all of the long rallies in the first two sets went the sixth-seeded Spanish left-hander's way.
But Berrettini turned it around midway through the third set. After not having a break point until then, Berrettini had three in the eighth game of the third set and converted his second, taking a 5-3 lead.
He then held serve in the next game on four consecutive points to send the match to a fourth set.
Nadal made the crucial tactical move midway through the fourth set when he retreated further behind the baseline when returning Berrettini's serve.
Berrettini had won more than 20 consecutive points on his serve at that point — and Nadal's move ended up being a stroke of genius.
From that moment on, Berrettini's first serve percentage dropped and Nadal pounced to secure the break of serve at 4-3.
It was a service game of huge drama as Berrettini defended two break points before he was ultimately made to pay the price for his first serve and forehand both deserting him when it mattered most.
Nadal's victory sees him become the fourth-oldest male player in history to play in the final of a grand slam.
It is his sixth Australian Open final, but he is still chasing his second title at Melbourne Park — an achievement that would make him just the fourth player to win all four grand slams two times.
- Agencies