Nikolay Davydenko, seeded 15th, beat No. 12 Albert Costa 6-3, 6-4 and will meet Canas in the semis.
Ferrer, seeded 11th, had the chance to close out the match when he served at 5-4 in the second. But Nadal, the 14th-seeded teenager, broke serve and fought back to win the tiebreaker.
Up a break of serve, Nadal served for the match at 5-4 but wasted three match points and couldn't hold. Ferrer turned the wild encounter again and clinched it on his second match point.
Ferrer will play Gaudio for a place in the final.
Dutch Open
Defending champion Nicolas Massu of Chile beat Tomas Behrend of Germany 6-2, 6-3 Friday to reach the semifinals of the Dutch Open.
He will play local favorite Martin Verkerk, who beat Spaniard David Sanchez 1-6, 7-6 (2), 6-4. After a shaky start, Verkerk's broke Sanchez in the seventh game of the third set without Sanchez winning a point.
Massu said his 1 1/2 hour match against Behrend was closer than the score reflected. But he said he felt at home on Amersfoort's clay court and was determined to defend his title.
Second seed Fernando Gonzalez of Chile beat Russia's Igor Andreev 6-3, 7-5 and will face another Dutchman, Dennis van Scheppingen, in the other semifinal.
Marcelo Rios, the first South American to reach No. 1 in ATP rankings history, retired from tennis on Friday because of an ongoing back injury.
"It is very sad for me to accept that I must leave tennis," said the Chilean left-hander, gifted on all surfaces.
"Tennis has been the passion of my life," he added. "I am 28, and I have dedicated almost 20 years to tennis. Tennis has been a way of life to me."
Rios has been largely inactive for about a year with recurrent back pain. He had surgery in Miami and in Santiago, but the problem was not solved.
"The truth is that I wanted to continue to play, and win a tournament for my daughter to see," Rios said. "That will not be possible."
Rios' daughter, Constanza, 3, lives with her mother in Costa Rica. Rios and his wife, Giuliana, are separated. Rios became No. 1 in the world in March 1998, soon after he reached his first and only grand slam final at the Australian Open, where he lost to Petr Koda of the Czech Republic. He held the ranking for six weeks, and led the ATP that year with seven titles in eight finals. He remains the only man to reach No. 1 without winning a grand slam title.
He was also the world's No. 1-ranked junior in 1993, after which he turned professional, earning more than US$9.7 million in prize money.
In his 10-year career, he won 18 singles titles in 31 finals, and one doubles title. However, he couldn't win his hometown event, losing the Santiago final three times, and in Vina del Mar last year.
Even so, he helped Chile win the World Team Cup last year for the first time, and finished with a Davis Cup record of 28-17 (25-10) in singles.
In 2000, Chile named him as its best athlete of the 20th century.
Rios, affectionately known as "Chino" by his countrymen, said he has not decided what he will do next but in recent months he has been working as a tennis commentator for a local radio station.
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