Peter Siddle has flown home from Australia's tour of the West Indies and James Pattinson will follow him at the conclusion of the second Test in Trinidad after both were ruled out of the third Test, due to begin in Dominica on Monday.

Pattinson and Siddle, team-mates for club, state and country, have both complained of back trouble in the past week. Siddle's was at first described as "back stiffness" and emerged as he played in the first Test in Barbados, quickly ruling him out of the second.

He and the rested Ryan Harris were replaced as fast bowlers for the second match by Pattinson, who was playing his first Test since he suffered a foot stress injury during the second Test against India at the SCG in January. However Pattinson struggled for rhythm and left the field on the third afternoon following a throw from the outfield.

Siddle was not considered for Australia's ODI team following his Test match success against India as the national selectors wished to retain his full and aggressive style for the game's longest form, while also keeping him fresher physically. Australia's captain Michael Clarke said the loss of Siddle and Pattinson would be difficult to cover, but was glad Harris had been left in reserve alongside Mitchell Starc.

"Disappointing we lose two very good bowlers," Clarke said. "But Mitchell Starc comes into contention now as one of our fast bowlers or we have the option to play two spinners again. Ryan Harris freshens up, doesn't play this Test and he's fresh and ready to go for the next Test. We've still got some options, it's just about looking at conditions when we get there and see what our best attack is."

Clarke said Pattinson had shown no signs of discomfort until he threw while off balance in the field and immediately complained of back stiffness. "No back issues until he did that," Clarke said. "I walked up to him and asked how you going and he said 'I'm a little bit stiff', told him to go and see the physio and it didn't get much better from there. He was still stiff the next morning, had a scan and we didn't get the results until late last night.

"Got those results and the decision was made this morning on what his plans were because it's more positive than negative. Obviously it's disappointing that he's not going to be available for the third Test but the reality is, if he's not going to be fit for the third Test, our best option for both him and Peter is to put them on a plane and get them home and get them stuck into treatment ASAP so they're fit for our next tour."

Australia's physio on tour, Kevin Sims, said Siddle's scans had shown a "low back bone stress injury" while Pattinson's "acute low back pain" will require further diagnosis on his return to Australia.

"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," Sims said. "He was subsequently ruled out of the second Test.

"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 for Australian duties.

"James Pattinson had an episode of acute low back pain after fielding and throwing awkwardly late on day three of the second Test. We have since monitored his condition over the last couple of days and the initial investigations suggest that while the injury is not serious there is insufficient time for him to recover to play in the third Test match.

"As such, we have today made the decision for James to return to Australia to prevent this injury developing any further and for him to receive the appropriate medical and physiotherapy management."

Neither bowler will be replaced on tour, leaving Ben Hilfenhaus, Harris and Starc as Australia's only available pacemen for the third Test.

Daniel Brettig is an assistant editor at ESPNcricinfo. He tweets here