DEFENDING champion Ivan Lendl moved a step closer to a fourth successive Marlboro Championships title when he entered the semi-finals at Victoria Park last night. An erratic but dominant 6-3, 6-4 victory over Peru's Jaime Yzaga enabled world number 18 Lendl to win the Gold Group, which also included France's Henri Leconte. Lendl joins top-seeded Swede Stefan Edberg, giant American Todd Martin and Dutchman Richard Krajicek in the last four of the $5.4 million event. Edberg, who sealed his semi-final place with a 4-6, 6-3, 7-6 (10-8) Red Group victory over Spain's Carlos Costa, and second-seeded Krajicek have been kept apart in the semi-finals. Martin won the Silver Group, beating South African Wayne Ferreira 6-4, 6-2 in his final match, and meets Edberg in today's opening semi-final. That will be followed by Lendl against the 11th-ranked Krajicek who became the first player to enter the last four on Thursday. Both Lendl and Edberg had trouble seeing the ball in vastly different conditions yesterday. Lendl said the bright floodlights in his evening match caused problems while Edberg, playing in scorching heat, complained about the shadows that fell on centre court. ''I couldn't see with the floodlights,'' said Lendl. ''Artificial lights are never as good as daylight. ''I was playing okay and did what I had to do. I think I'm hitting the ball well enough to win the tournament but it is a question of concentration.'' Edberg, who fell 4-0 behind in the first set, said the conditions were different to when he beat Australian Todd Woodbridge in his opening group match. ''I had trouble with the shadows and couldn't see the ball,'' said Edberg. ''It was better when I played Todd because then it was overcast.'' The Swede, ranked sixth in the world, needed only five games to assure himself of a semi-final place. Edberg lost his serve twice at the start of the match, but then rallied and recovered one break to trail 5-4. But Costa still had the break advantage to win the set. Fortunes were reversed in the second set with Edberg taking a 4-0 lead, breaking twice and losing his own serve once before levelling the match at one set all. At that stage, the match was over in terms of deciding the Red Group winner, and with the pressure taken off both players, the entertainment increased. A break each took the match into a tie-break with Edberg sneaking through 10-8. In the doubles competition, Australia's world champions Todd Woodbridge and Mark Woodforde beat the popular American-French pairing of John McEnroe and Leconte to win the Scorpio Group with three victories.