PORT OF SPAIN  - Australian fast bowlers Peter Siddle and James Pattinson have been ruled out of next week's final Test against West Indies and will return home immediately because of back pain.

Cricket Australia said Siddle, who also missed this week's second Test in Trinidad, would fly home on Thursday while Pattinson would follow him 24 hours later once the second Test ends.

"Peter Siddle developed some back soreness late in the first Test against the West Indies and scans conducted in Trinidad showed the early signs of a low back bone stress injury," Australian team physiotherapist Kevin Sims said.

"He was subsequently ruled out of the second Test and after further consultation we feel that to prevent this injury developing any further it is in Peter's best interest for him to return to Australia to rest and for appropriate physiotherapy to ensure he is fully fit when next selected."

Pattinson was chosen for the second Test but hurt his lower back on Tuesday while fielding. A team spokesman said he would be available to bat, if required, on the final day on Thursday but was unlikely to bowl.