INJURY CONCERNS At this stage, it's unlikely they'll take any further part here Australia coach John Buchanan on injured duo Jason Gillespie and Stuart MacGill

Zimbabwe were facing an innings defeat after Australia enforced the follow-on and held a formidable 409-run lead with two days to play in Perth.

Jason Gillespie (3-52) starred as the visitors were bowled out for 239, but he and Stuart MacGill were injured.

Opener Trevor Gripper hit 53 and Craig Wishart 46 before the tail crumbled with the last six wickets going for 40.

The visitors reached 87-2 in their second innings at stumps, with Mark Vermeulen unbeaten on 50.

Gillespie took both wickets but bowled just three overs before succumbing to a side strain and leaving the field.

Leg-spinner MacGill joined him on the sidelines after breaking down with a calf muscle complaint.

"Once the diagnostics have been done and everyone does the assessment, obviously, we'll know more about the following Test match," Australia coach John Buchanan said

Zimbabwe resumed play on day three on 79-1 and trailing by a massive 656 runs after Matthew Hayden recorded the highest ever Test score in Australia's 735-6 declared.

Gillespie was in sterling form prior to injuring his side

Gripper was the first to go, caught by Darren Lehmann off Brett Lee (3-48) soon after registering his fourth Test half-century.

Zimbabwe quickly fell from 120-2 to 131-4 when MacGill (2-54) removed Stuart Carlisle and Vermeulen with catches to Hayden.

Wishart and Craig Evans, playing his third Test and first for five years, then added 68 runs in a promising fifth-wicket stand.

But the collapse started when Andy Bichel (2-62) had Wishart caught behind by Adam Gilchrist to reduce Zimbabwe to 199-5.

Bichel followed up with the scalp of Evans (22) in his next over, paving the way for Lee and Gillespie to run through the tail with a minumim of fuss.

Home captain Steve Waugh predictably enforced the follow-on, and it was Gillespie to the fore again as the visitors descended to 11-2.

Gripper fell caught behind in the second over for a duck before fellow opener Dion Ebrahim played on offering no sort of defensive shot.

Vermeulen, who brought up his second Test fifty on the stroke of stumps, was well-supported by Carlisle (26 not out), but it is a losing battle Zimbabwe are fighting.

Australia: SR Waugh (capt), RT Ponting, AJ Bichel, AC Gilchrist, JN Gillespie, ML Hayden, JL Langer, B Lee, DS Lehmann, SCG MacGill, DR Martyn.