The 23-year-old Essex player won his delayed second-round match with the Slovakian Karol Kucera
6-3, 6-1 but then succumbed to Germany's Hendrik Deekman 6-4, 4-6, 6-4 in the quarter-finals.
But, with bonuses for beating the world No 2, Stich, Petchey will have gained enough computer points to propel him well above his current placing of 122 when the new rankings are issued next week. This will virtually guarantee him direct entry for the French Open in Paris without the need to qualify.
Petchey's reversal of fortunes has been startling after his dismal display in Britain's 4-1 Davis Cup humbling by Portugal last weekend. On Oporto clay he lost both his singles rubbers to lower-ranked players in straight sets and suffered a loss of confidence in the doubles which Britain only won thanks to the experience of Jeremy Bates.
Richard Lewis, director of national training at the Lawn Tennis Association, said of Petchey's performances on South African hard courts: 'It just underlines the problems British players have of playing on clay.'
Meanwhile, Switzerland's Jakob Hlasek knocked out the third seed, Thomas Muster, of Austria, to leave the Russian, Alexander Volkov, the only seeded player to qualify for the South African semi-finals. Hlasek dismissed Muster 6-7, 6-4, 6-2 and the sixth-seeded Volkov also needed three sets to get past South Africa's Marcos Ondruska 2-6, 6-2, 6-4.
In the quarter-finals of the Salem Open in Osaka, the defending champion, Michael Chang, bowed out while the world No 1, Pete Sampras, powered on irresistibly.
The fifth-seeded Andre Agassi was leading his fellow American, David Wheaton, 7-6, 3-1 when rain brought the day's play to a premature close. The match, which will determine who meets Sampras in the semi-finals, resumes today.
The other semi-final will pit Henrik Holm of Sweden, who took full advantage of Chang's erratic play, against Lionel Roux from France, the world's 210th-ranked player who has claimed two big scalps in two days.
Chang, the crowd's favourite, relinquished his title in disappointing fashion, Holm, ranked 52nd in the world, taking the match 2-6, 7-5, 6-3.
Twenty-four hours after ousting Ivan Lendl, Roux scored another big upset by eclipsing Aaron Krickstein 7-5, 7-6.