Nadal will take heart from his 5-1 head-to-head record against the Croatian 29-year-old, who won their first meeting in 2009 but has since struggled against the powerful left-hander.
"In the second set I tried to shift the momentum and once I broke him in the last game of the second set I took control of the match".
Third seed Grigor Dimitrov, survivor of a fourth-round thriller against home favourite Nick Kyrgios, will also be in action against the sole surviving Briton, Kyle Edmund. "She's fighting every ball".
Suarez Navarro wound up her unsafe one-handed backhand with great effect, going a break up at 3-2 after Wozniacki made a couple of errors under pressure, but squandered that advantage by drilling a backhand wide to be pegged back at 4-4.
"You know, she's been playing well, definitely", she said.More news: Undertaker returns to Raw
Serving at 4-5 Suarez Navarro, who was in her sixth Grand Slam quarter-final and third in Australia but had never progressed further, saved a match point before taking it to a third on her first set point in the tiebreak. It was a little stressy at the end but I played my game and it went well today.
Rafael Nadal knows his path to a 17th grand slam title will only get tougher after a relatively routine run of opponents since his French Open triumph last June when he lines up against Marin Cilic in Tuesday's Australian Open quarter-final.
Mertens is the first Belgian player to reach the semi-finals here since former champion Kim Clijsters, at whose academy she trains, in 2011.
Wozniacki will face another unseeded player, Elise Mertens of Belgium, on Thursday for a place in the final.
"It's lovely to hear them (milestones)".More news: Price Performance Review on Shares of Pioneer Natural Resources Co (PXD)
World number two Caroline Wozniacki needed just over an hour to beat Slovakia's Magdalena Rybarikova 6-3 6-0 in the fourth round.
They have faced each other seven times before with Wozniacki leading 5-2.
World No.2 Caroline Wozniacki will look to continue her charge towards the top spot in the Australian Open quarter-finals against Carla Suarez Navarro.
The temperature was 25 degrees Celsius (77F) and forecast to reach a top of 26.More news: Interpublic Group of Companies Target of Unusually Large Options Trading (IPG)