Michael Chang, the 16-year-old sensation from Placentia who had eliminated second-seeded Jimmy Connors from the $350,000 Volvo Indoor tournament in Chicago, took himself out of the event Friday because of tendinitis in his right leg.
His opponent, Horatio De La Pena of Argentina, advanced to today's semifinal round where he will meet the winner of Friday's quarterfinal match between John McEnroe and Brad Gilbert.
It was the second free pass for De La Pena in the six-day event. He won by default against Aaron Krickstein, who had to withdraw Wednesday due to tendinitis in the right elbow.
"I am very sorry to have to leave Chicago," Chang said in an statement issued by tournament officials. "I have been playing well."
Chang had problems with his leg before arriving in Chicago. And, on Thursday night, when he beat Connors, 6-3, 7-6, he aggravated the condition.
Chang, who is scheduled to play in the Memphis Indoors championships Monday, had to sit down after getting behind, 6-5, in the second set when he failed to hold serve.
Tim Mayotte, seeded fourth, took a big step toward his third straight Chicago title by overpowering Andres Gomez, 6-3, 6-1, in a quarterfinal match.
Top-seeded Conchita Martinez of Spain beat Liz Smylie of Australia, 6-3, 6-1, to advance to the semifinals of a $50,000 women's tournament at Wellington, N.Z.
Also advancing were Leigh Anne Eldredge of Altadena, fifth-seeded Sandra Wasserman of Belgium and JoAnne Faull of Australia. Eldridge beat Martina Pawlik of West Germany, 7-5, 6-2, and will play Martinez in the semifinals.
Wasserman beat second-seeded Belinda Cordwell of New Zealand, 6-7, 7-5, 6-3, and Faull beat Halle Cioffi of Knoxville, Tenn., 6-3, 6-3.