# 2003 Siebel Open – Singles

The 2003 Siebel Open was a men's international tennis tournament. Lleyton Hewitt was the defending champion but did not compete that year.
Andre Agassi won in the final 6–3, 6–1 against Davide Sanguinetti.

## Seeds

A champion seed is indicated in bold text while text in italics indicates the round in which that seed was eliminated.
* Andre Agassi (champion)
* Paradorn Srichaphan (first round)
* James Blake (semifinals)
* Jan-Michael Gambill (second round)
* Todd Martin (second round)
* Davide Sanguinetti (final)
* Nikolay Davydenko (quarterfinals)
* Kenneth Carlsen (quarterfinals)

## Draw
### Key

* Q = Qualifier
* WC = Wild card
* LL = Lucky loser
* Alt = Alternate
* SE = Special exempt
* PR = Protected ranking
* ITF = ITF entry
* JE = Junior exempt
* w/o = Walkover
* r = Retired
* d = Defaulted
* SR = Special ranking
| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final |
| 1 | A Agassi | 6 | 6 | | | | | | | | | | | | | | | | | | | | |
| WC | M Chang | 4 | 2 | | 1 | A Agassi | 6 | 6 | | | | | | | | | | | | | | | |
| WC | M Philippoussis | 3 | 6 | 6 | WC | M Philippoussis | 4 | 1 | | | | | | | | | | | | | | | |
| | J-R Lisnard | 6 | 3 | 3 | | | | | | 1 | A Agassi | 6$^3$ | 7$^8$ | 6 | | | | | | | | | |
| | J Vacek | 4 | 2 | | | | | | | | V Voltchkov | 7$^7$ | 6$^6$ | 1 | | | | | | | | | |
| | V Voltchkov | 6 | 6 | | | V Voltchkov | w/o | | | | | | | | | | | | | | | | |
| | B Vahaly | 4 | 3 | | 5 | T Martin | | | | | | | | | | | | | | | | | |
| 5 | T Martin | 6 | 6 | | | | | | | | | | | | 1 | A Agassi | 6 | 6 | | | | | |
| 3 | J Blake | 6 | 6 | | | | | | | | | | | | 3 | J Blake | 4 | 2 | | | | | |
| WC | W Black | 2 | 4 | | 3 | J Blake | 6 | 6 | | | | | | | | | | | | | | | |
| | T Dent | 2 | 6$^5$ | | | H-T Lee | 3 | 2 | | | | | | | | | | | | | | | |
| | H-T Lee | 6 | 7$^7$ | | | | | | | 3 | J Blake | 7 | 6 | | | | | | | | | | |
| | K Pless | 6 | 1 | 4 | | | | | | 7 | N Davydenko | 5 | 2 | | | | | | | | | | |
| | R Ginepri | 4 | 6 | 6 | | R Ginepri | 4 | 6 | 3 | | | | | | | | | | | | | | |
| | J Morrison | 3 | 6 | 6$^1$ | 7 | N Davydenko | 6 | 3 | 6 | | | | | | | | | | | | | | |
| 7 | N Davydenko | 6 | 2 | 7$^7$ | | | | | | | | | | | | | | | | 1 | Andre Agassi | 6 | 6 |
| 6 | D Sanguinetti | 6 | 6$^7$ | 6 | | | | | | | | | | | | | | | | 6 | Davide Sanguinetti | 3 | 1 |
| | Ž Krajan | 2 | 7$^9$ | 1 | 6 | D Sanguinetti | 7$^7$ | 7 | | | | | | | | | | | | | | | |
| | M Fish | 6 | 4 | 7$^7$ | | M Fish | 6$^1$ | 5 | | | | | | | | | | | | | | | |
| Q | D Tursunov | 2 | 6 | 6$^3$ | | | | | | 6 | D Sanguinetti | 6 | 7 | | | | | | | | | | |
| | V Spadea | 6 | 6 | | | | | | | | V Spadea | 1 | 5 | | | | | | | | | | |
| | L Burgsmüller | 3 | 4 | | | V Spadea | 6 | 6 | | | | | | | | | | | | | | | |
| Q | T Reid | 2 | 0 | | 4 | J-M Gambill | 3 | 3 | | | | | | | | | | | | | | | |
| 4 | J-M Gambill | 6 | 6 | | | | | | | | | | | | 6 | D Sanguinetti | 6 | 6$^2$ | 6 | | | | |
| 8 | K Carlsen | 7 | 3 | 7$^7$ | | | | | | | | | | | | J Gimelstob | 4 | 7$^7$ | 3 | | | | |
| | M Norman | 5 | 6 | 6$^3$ | 8 | K Carlsen | 6 | 3 | 7 | | | | | | | | | | | | | | |
| Q | P Goldstein | 6 | 2 | 6 | Q | P Goldstein | 2 | 6 | 5 | | | | | | | | | | | | | | |
| | J Balcells | 2 | 6 | 3 | | | | | | 8 | K Carlsen | 3 | 4 | | | | | | | | | | |
| | M Llodra | 7$^7$ | 1 | 1 | | | | | | | J Gimelstob | 6 | 6 | | | | | | | | | | |
| Q | Z Fleishman | 6$^4$ | 6 | 6 | Q | Z Fleishman | 1 | 4 | | | | | | | | | | | | | | | |
| | J Gimelstob | 7 | 6 | | | J Gimelstob | 6 | 6 | | | | | | | | | | | | | | | |
| 2 | P Srichaphan | 5 | 2 | | | | | | | | | | | | | | | | | | | | |