The former Australia international, 41, headed to Stamford Bridge last summer on a free transfer from west London neighbours Fulham to offer back-up to Petr Cech.
He made 12 starts and a single substitute appearance - in the Champions League semi-final first leg against Atletico Madrid.
Earlier this week, Chelsea confirmed the departure of Portuguese goalkeeper Hilario at the end of his contract.
Defender Ashley Cole also leaves Chelsea this summer, along with England midfielder Frank Lampard.
However, Blues manager Jose Mourinho has already started to rebuild his squad with the signing of former Arsenal captain Cesc Fabregas from Barcelona and Atletico Madrid's Spain international forward Diego Costa - rated at around B£32million - is another well-documented target.
- Sports & Recreation
- Atletico Madrid