Estadísticas del jugador contra cada club rival
| Equipo | PJ | V | E | D | G | A | ||
|---|---|---|---|---|---|---|---|---|
 Malmö FF | 2 | 0 | 1 | 1 | 0 | 0 | 0 | 0 |
 Valletta | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 0 |
 Shamrock Rovers | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 |
 Cork City | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 |
 Bohemians | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 |
 Dynamo Kyiv | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 |
 Limerick | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
 Shelbourne | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 |
 Sligo Rovers | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 |
 Finn Harps | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
 Derry City | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
 St Patrick's | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 |
 Longford Town | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
 Dundalk | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 |
 Waterford United | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
 UCD | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 |
 Athlone Town | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 0 |
 Levadia | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
 Shakhtyor | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 |
 Salthill Devon | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
Declan O'Brien ha marcado 64 goles en 116 partidos profesionales en 4 clubes. Entre los clubes por los que ha pasado — Drogheda United, Carrick Rangers, Monaghan United, St Patrick's — Declan O'Brien fue más prolífico en el Drogheda United, donde anotó 47 goles en 76 partidos. Declan O'Brien mide 180 cm.
