The most famous match of El Aynaoui's career came in the quarter-finals of the Australian Open in 2003. In the Round of 16, El Aynaoui defeated the World No. 1, Lleyton Hewitt, 6–7, 7–6, 7–6, 6–4, in a very high quality match, thus setting up a quarter-final showdown with the up-and-coming American Andy Roddick (who would reach the World No. 1 ranking later that year). The five-set, five-hour match included the then longest fifth set in Grand Slam tennis history (since surpassed by the marathon Wimbledon 2010 match between John Isner and Nicolas Mahut). Roddick won the battle 4–6, 7–6, 4–6, 6–4, 21–19. Both players saved match points before the fifth set ended. El Aynaoui's one match point came in the tenth game of the fifth set, with Roddick serving at 4–5. Roddick saved the match point with a cross-court forehand winner after a short rally. Roddick broke El Aynaoui's serve at 10–10 to go up 11–10 and serve for the match, but El Aynaoui broke straight back for 11–11. Roddick broke El Aynaoui's serve again at 19–19 to serve for the match for the second time at 20–19, with Roddick clinching the match on his second match point.