Truth is, there were not many the rest of the way, as Nadal finished with 35 winners and just 19 unforced errors. Del Potro had forced six break points during the first set but the Spaniard fended each one off.
Del Potro, the US Open victor in 2009, is playing the tournament for only the second time since 2012 after a spate of injuries. Injuries have hampered the King of Clay throughout the past year. He was not playing his best tennis.
I played two sets at the same level as Dominic Thiem. Nadal is 49-0 against everyone else on his preferred surface in 2017 and 2018.
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.
But Nadal's domination on the Roland Garros clay, where his record now stands at 85-2, is without equal and he will be a huge favourite to beat Grand Slam final debutant Thiem.
Earlier, the Japanese duo won 6-2, 6-2 against Hao-Ching Chan of Taiwan and Zhaoxuan Yang of China 6-2, 6-2.
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Thiem led 6-3 but suddenly lost focus. He then battled past Tsitsipas 6-2 2-6 6-4 6-4 and Berrettini 6-3 7-6 6-3 6-2 to reach the fourth round. Both players dropped serve four times.
Leading the tiebreak 6-3, he was powerless as Cecchinato claimed the following four points to earn the first of three set points.
Cecchinato had never won a Grand Slam match before this year's Roland Garros but made the semis with a string of stunning wins.
"It's tough to speak now", said an emotional Del Potro.
Marach and Pavic are going for their second straight major title together after winning the Australian Open in January.
The unseeded Hozumi and Ninomiya were the first all-Japanese duo to reach a Grand Slam final in women's doubles. On the second, Thiem defeated Nadal 7-5, 6-3.
He broke the Austrian in the third game of the set.
Nadal, a 16-time Grand Slam champion, claimed his 85th win here against just two losses after weathering a big-hitting opening from 2009 US Open victor Del Potro to win 6-4, 6-1, 6-2.
In 2016, Cecchinato was accused of match-fixing and suspended for 18 months, but he appealed, and his punishment was dropped on a technicality.
"He beat me in Madrid and he has incredible power", said Nadal ahead of their French Open final. Their semifinal is later Friday.
At least Thiem has in the past found the key to unravelling the Nadal clay court enigma. He held the game with a combination serve and volley victor.
The boys' final at the French Open will pit top-seeded Sebastien Baez of Argentina against Chun Hsin Tseng from Taiwan.
"Forget the 10 (French Open titles) and forget what happened past year, Thiem has to remember what happened in Madrid which is a title Nadal wants to win nearly as much as the French", Wilander, Eurosport's chief analyst, told Reuters. Thiem remains in search of his first career major tournament title.
He said: "What you did and what you're doing it's one of the most awesoming things that (an) athlete ever achieved in sports, to win this tournament 11 times".
Dominic Thiem of Austria volleys during the men's singles semi-final match against Marco Cecchinato of Italy.