# 2003 AIG Japan Open Tennis Championships – Men's singles

Kenneth Carlsen was the defending champion but lost in the third round to Hyung-Taik Lee.
Rainer Schüttler won in the final 7–6$^{(7–5)}$, 6–2 against Sébastien Grosjean.

## Seeds

All sixteen seeds received a bye to the second round.
* Rainer Schüttler (champion)
* Sébastien Grosjean (final)
* Paradorn Srichaphan (semifinals)
* Jiří Novák (third round)
* Mark Philippoussis (quarterfinals)
* Nicolas Kiefer (third round)
* Hyung-Taik Lee (quarterfinals)
* Jan-Michael Gambill (quarterfinals)
* Kenneth Carlsen (third round)
* Mario Ančić (third round)
* n/a
* John van Lottum (second round)
* Brian Vahaly (second round)
* Wesley Moodie (second round)
* Lars Burgsmüller (second round)
* Grégory Carraz (second round)

## 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

### Finals

| Semifinals | Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final |
| 1 | Rainer Schüttler | 6 | 6 | | | | | |
| | Cyril Saulnier | 3 | 2 | | | | | |
| | Cyril Saulnier | 3 | 2 | | 1 | Rainer Schüttler | 7$^7$ | 6 |
| | | | | | 2 | Sébastien Grosjean | 6$^5$ | 2 |
| 3 | Paradorn Srichaphan | 6 | 3 | 4 | 2 | Sébastien Grosjean | 6$^5$ | 2 |
| 2 | Sébastien Grosjean | 4 | 6 | 6 | | | | |

### Top half
#### Section 1

| First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Third round | Third round | Third round | Third round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals |
| | | | | 1 | R Schüttler | 6 | 6 | | | | | | | | | |
| WC | S Iwabuchi | 7$^7$ | 6 | WC | S Iwabuchi | 0 | 4 | | | | | | | | | |
| | C Mamiit | 6$^4$ | 2 | | | | | | 1 | R Schüttler | 6 | 6 | | | | |
| | R Kendrick | 7$^7$ | 6 | | | | | | | R Kendrick | 3 | 2 | | | | |
| | W Arthurs | 6$^3$ | 4 | | R Kendrick | 6 | 3 | 6 | | | | | | | | |
| | | | | 13 | B Vahaly | 2 | 6 | 4 | | | | | | | | |
| | | | | | | | | | | | | | 1 | R Schüttler | 6 | 6 |
| | | | | | | | | | | | | | | S Draper | 3 | 3 |
| | | | | LL | E Taino | 2 | 6$^5$ | | | | | | | | | |
| Q | J Vacek | 3 | 6$^4$ | | S Draper | 6 | 7$^7$ | | | | | | | | | |
| | S Draper | 6 | 7$^7$ | | | | | | | S Draper | 7 | 6 | | | | |
| | I Heuberger | 2 | 6$^1$ | | | | | | 6 | N Kiefer | 5 | 2 | | | | |
| | A Bogomolov Jr. | 6 | 7$^7$ | | A Bogomolov Jr. | 5 | 6$^7$ | | | | | | | | | |
| | | | | 6 | N Kiefer | 7 | 7$^9$ | | | | | | | | | |

#### Section 2

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Third round | Third round | Third round | Third round | Third round | Quarterfinals | Quarterfinals | Quarterfinals |
| | | | | | 4 | J Novák | 7$^7$ | 6 | | | | | | | | |
| Q | B Phau | 6$^1$ | 7$^7$ | 7$^7$ | Q | B Phau | 6$^2$ | 2 | | | | | | | | |
| | J Salzenstein | 7$^7$ | 6$^4$ | 6$^3$ | | | | | 4 | J Novák | 6 | 5 | 4 | | | |
| | J Gimelstob | 6$^5$ | 6 | 1 | | | | | | C Saulnier | 4 | 7 | 6 | | | |
| | C Saulnier | 7$^7$ | 3 | 6 | | C Saulnier | 7$^8$ | 7$^7$ | | | | | | | | |
| | | | | | 15 | L Burgsmüller | 6$^6$ | 6$^4$ | | | | | | | | |
| | | | | | | | | | | | | | | | C Saulnier | 5 |
| | | | | | | | | | | | | | | 5 | M Philippoussis | 2$^r$ |
| | | | | | 10 | M Ančić | 6 | 7 | | | | | | | | |
| | W Eschauer | 0 | 4 | | Q | T Iwami | 2 | 5 | | | | | | | | |
| Q | T Iwami | 6 | 6 | | | | | | 10 | M Ančić | 4 | 5 | | | | |
| | F Browne | 6 | 6 | | | | | | 5 | M Philippoussis | 6 | 7 | | | | |
| WC | T Terachi | 3 | 4 | | | F Browne | 4 | 3 | | | | | | | | |
| | | | | | 5 | M Philippoussis | 6 | 6 | | | | | | | | |

### Bottom half
#### Section 3

| First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Third round | Third round | Third round | Third round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals |
| | | | | 7 | H-T Lee | 6 | 6$^3$ | 6 | | | | | | | | | |
| Q | G Weiner | 4 | 2 | | F Verdasco | 3 | 7$^7$ | 3 | | | | | | | | | |
| | F Verdasco | 6 | 6 | | | | | | 7 | H-T Lee | 6 | 6 | | | | | |
| | M Vassallo Argüello | 0 | 3 | | | | | | 9 | K Carlsen | 3 | 4 | | | | | |
| WC | G Motomura | 6 | 6 | WC | G Motomura | 2 | 6$^4$ | | | | | | | | | | |
| | | | | 9 | K Carlsen | 6 | 7$^7$ | | | | | | | | | | |
| | | | | | | | | | | | | | 7 | H-T Lee | 6 | 6$^5$ | 3 |
| | | | | | | | | | | | | | 3 | P Srichaphan | 4 | 7$^7$ | 6 |
| | | | | 14 | W Moodie | 1 | 6$^3$ | | | | | | | | | | |
| | A Waske | 6$^5$ | 3 | WC | T Suzuki | 6 | 7$^7$ | | | | | | | | | | |
| WC | T Suzuki | 7$^7$ | 6 | | | | | | WC | T Suzuki | 2 | 6$^3$ | | | | | |
| | D Norman | 7 | 6 | | | | | | 3 | P Srichaphan | 6 | 7$^7$ | | | | | |
| Q | G Bastl | 5 | 4 | | D Norman | 6 | 6$^3$ | 6$^2$ | | | | | | | | | |
| | | | | 3 | P Srichaphan | 4 | 7$^7$ | 7$^7$ | | | | | | | | | |

#### Section 4

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Third round | Third round | Third round | Third round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals |
| | | | | | 8 | J-M Gambill | 6 | 6 | | | | | | | | | |
| | I Miranda | 6 | 4 | 4 | | B Ulihrach | 3 | 4 | | | | | | | | | |
| | B Ulihrach | 2 | 6 | 6 | | | | | | 8 | J-M Gambill | 6 | 7 | | | | |
| | T Berdych | 6$^2$ | 6 | 3 | | | | | | Q | M Kratochvil | 3 | 5 | | | | |
| Q | M Kratochvil | 7$^7$ | 4 | 6 | Q | M Kratochvil | 6 | 6 | | | | | | | | | |
| | | | | | 12 | J van Lottum | 2 | 3 | | | | | | | | | |
| | | | | | | | | | | | | | | 8 | J-M Gambill | 3 | 6$^4$ |
| | | | | | | | | | | | | | | 2 | S Grosjean | 6 | 7$^7$ |
| | | | | | 16 | G Carraz | 5 | 6 | 5 | | | | | | | | |
| | A Vinciguerra | 6 | 4 | 1 | | D van Scheppingen | 7 | 1 | 7 | | | | | | | | |
| | D van Scheppingen | 4 | 6 | 6 | | | | | | | D van Scheppingen | 3 | 6$^3$ | | | | |
| | R Söderling | 4 | 4 | | | | | | | 2 | S Grosjean | 6 | 7$^7$ | | | | |
| | I Karlović | 6 | 6 | | | I Karlović | 3 | 6$^8$ | | | | | | | | | |
| | | | | | 2 | S Grosjean | 6 | 7$^{10}$ | | | | | | | | | |