There is no such thing as a sure thing in the world of sports betting.

According to a report from ESPN’s David Payne Purdum, a bettor at a sports book in Las Vegas decided it was a good idea to risk $8,500 on tennis legend Novak Djokovic at -8,500 odds to get past Denis Istomin in the second round of the Australian Open on Thursday.

A Djokovic victory would have netted the gambler just $100. Istomin was a huge underdog versus the man who has won 12 grand slam singles titles and is considered one of the best in the game’s history.

Istomin was ranked no. 117 in the world (Djokovic was no. 1), and ended up winning 7-6 (10-8) 5-7 2-6 7-6 (7-5) 6-4. His win was only the second time someone outside the top 100 has beaten Djokovic in the last seven years, according to a CNN report.

What is also amazing is that Istomin’s lifetime record against top-10 players is 1-32.