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.
"True, I understand that everybody here, you have to write things", he said. Cecchinato, who upset Novak Djokovic in the quarterfinals after winning two pulsating tiebreaks, rallied and even held three set points prior to Thiem triumphing 12-10.
The Austrian was in control of his semi-final against the world number 72, holding three set points in a tie-break for a 2-0 lead.
Nadal is bidding to become only the second player to win 11 titles at any Grand Slam tournament after Margaret Court, who won the Australian women's singles title 11 times.
The No. 7-seeded Thiem, a 24-year-old from Austria, is appearing in his first Grand Slam final.
Thiem's fighting spirit was evident in abundance - he continued to put pressure on Nadal through his return game, while consistently scrapping to stave off perilous positions on his own serve - but ultimately the Spaniard's quality and, often, his sheer force of will, won the day.
The Czech pair beat second-seeded Andrea Sestini Hlavackova and Barbora Strycova 6-3, 6-2.
The injury-prone Argentine had a discussion with Dr. Bernard Montalvan during the changeover, with Nadal leading 3-2 in the first set.
Del Potro insisted his hip had not troubled him during the match, instead putting the defeat down to one simple fact: "His game is too good for me".
Up in the stands, Nadal's uncle Toni, his former coach, was nervous, too, "because I thought maybe we can have a problem", he said.
"The big key was the second-set tie-break because it was very close and I saved I think three set points", said Thiem.
The 24-year-old Austrian, playing his first Grand Slam final, made 18 unforced errors in losing the first set, and hit 11 clean winners.
Thiem‚ who was playing in his third successive French Open semi-final‚ admitted the second set had been a nervy encounter after needing five set points to get through it.
Nadal will retain the world number one ranking if he wins - but that will be the last thing on his mind. The French Open, like all Grand Slam tournaments, is best-of-five for men.
Rafael Nadal has taken the first set of his French Open final against Dominic Thiem.
A few hours earlier, as Nadal and Thiem warmed up, the booming voice of the announcer at Court Philippe Chatrier detailed the bona fides of both. "When (Thiem) is dominating the point, he is very unsafe".
Del Potro will be his opponent on Friday after eliminating No. 3 seed Marin Cilic 7-6 (5), 5-7, 6-3, 7-5 to make into the semifinals for the first time since 2009.
He is the only man to beat Nadal on clay over the past two seasons, doing so twice.
The forecast says there is a chance of rain.