Boris Becker, playing like a clay-court specialist, downed defending champion Andrei Chesnokov of the Soviet Union 6-1, 6-3 Friday to reach the semifinals of the Monte Carlo Open.

Becker will meet Yugoslavia's Goran Prpic, who eliminated Carl-Uwe Steeb 6-4, 6-2 in the first quarterfinal of the day.Horst Skoff of Austria topped Jonas Svenson of Sweden 6-3, 6-3 and Sergi Brugera of Spain edged Magnus Gustafsson of Sweden 7-5, 7-5 in the other quarterfinals.

Becker is slowly improving his game on clay after winning Grand Slam titles on grass at Wimbledon and hardcourts at the U.S. and Australian Opens.

He kept Chesnokov off balance by varying the pace and length of his shots.

"It was one of my best matches on clay," Becker said. "I'm playing every match better and better."

It took Becker only nine minutes to grab a 3-0 lead over Chesnokov and only 30 minutes to win the first set.

Becker hit a lot of short balls, bringing Chesnokov to the net and then passing him or forcing volleying errors.

"I was suprised that he knew the tactics against me, hitting slices and drop shots," Chesnokov said.

Becker, who likes to rush the net on faster surfaces, stayed near the baseline and came in only following his serve, letting Chesnokov make the mistakes.

Occasionally Becker even blasted a backhand winner past Chesnokov at the baseline.

"Sometimes he played like a god," Chesnokov said.

In the second set, each player held serve until Becker broke for a 4-2 lead.

At Barcelona, Spain, top seed Martina Navratilova was upset by Nathalie Tauziat of France 6-1, 6-4 Friday in the quarterfinals of the WTA Open.

Navratilova, ranked fourth in the world and favored to win the tournament, won the completion of a rain-interrupted match earlier in the day, defeating Katia Piccolini of Italy 6-0, 6-2.