Rehmann was a successful junior player, winning the Boys' Doubles at the 1993 Australian Open, with countryman Christian Tambue.

Along the way he and partner Alexander Mronz were victorious over top seeds Todd Woodbridge and Mark Woodforde.

In 1994, he partnered Australian Joshua Eagle at the Wimbledon Championships but they lost in the opening round to number six seeds Tom Nijssen and Cyril Suk.

He defeated Luiz Mattar of Brazil 6–3, 6–4, 6–1 and make it into the second round, but then lost to eventual quarter finalist Andriy Medvedev 5–7, 4–6, 1–6.

In Seoul he reached another ATP final but was defeated again, this time to Greg Rusedski.