Nadal has a 9-5 head-to-head record against del Potro.
Wilander believes Thiem can worry Nadal if he is prepared to "take risks" like Diego Schwartzman did in the quarter-finals when he snapped the left-hander's run of 37 consecutive completed sets won at the French Open by snatching the opener. "It doesn't matter what sport". "This is why the guy was dominating clay-court tennis over the last 14 years like nobody else before".
He didn't stop there, such was his extended praise for the recently turned 32-year-old. Good thing is I played a lot of good matches this clay-court season.
Argentina's Juan Martin del Potro on Thursday qualified for the semifinals of the French Open after he defeated Marin Cilic of Croatia 7-6, 5-7, 6-3, 7-5 in a two-day rain-delayed match.
Thiem has been to the semifinals in Paris three years in a row.
Yet Bresnik obviously isn't throwing in the towel.
Thiem is the only man to beat Nadal on clay in the last two seasons - in Madrid this year and Rome in 2017.
The Spaniard continued his extraordinary domination at Roland Garros with a ruthless 6-4 6-3 6-2 victory.
Thiem, who beat Nadal in Madrid this season, Rome past year and in Buenos Aires on clay in 2016, trails 3-6 in the pair's head-to-head.
Nadal is now 110-2 in best-of-five-set matches on the surface, 85-2 in Paris.
"He's a big favorite against everybody", he told reporters.
"But after the loss, I go a little bit down with mental, and physically I play so many matches, so I think is normal".
"But I have a plan".
The world number one held serious discussions with coach Carlos Moyá in an intense session in the heat as he studiously went about his business.
Nadal acknowledged that Thiem has been a "very complex" opponent.
If not, it will be Goodnight Vienna for the man with one of the best single-handed backhands in tennis. "He has the power".
This was the No 5-seeded del Potro's first semifinal at Roland Garros since 2009. Or at least not a blowout. He has undergone four wrist surgeries but the issue, thankfully, was a minor hip complaint. After guzzling water during that break, Nadal felt better and was back to playing his unmistakable brand of almost unbeatable clay-court tennis.
But Austrian Thiem will see this as a fantastic opportunity to reach a maiden Grand Slam final, after losing to Djokovic and Nadal at the semi-final stage in each of the last two years in Paris.
"The first set was very hard, there were lots of opportunities for Juan Martin del Potro and I was perhaps a little lucky to win it", Nadal said afterwards. After serving a fault, Nadal took the unusual step of heading to the sideline in the middle of a game.
And on the penultimate point of the semifinal, after being run ragged, the 2009 US Open victor could only offer up a smile.
Once Nadal stole the opener with a break in the 10th game, it was one-way traffic. He impressively recovered from a slow start to make the first set close.
The first set was a tight affair, with Thiem claiming the decisive break in the 11th game but the Italian retained his composure to send the second to a tie-break.
"I can not believe it now", Karin Thiem, a tennis coach, told a group of reporters. I know he has great potential.
Anything can happen in a Grand Slam final.
"I think if I'm facing Rafa, I'm not the one who has the pressure".
The smile never left her face.
He concluded, however, by saying: "It's not easy".
"I came here without big expectations, just seeing how my body feels match by match".