First-choice ruckman Nic Naitanui (achilles) remains in doubt for Saturday's opener against North Melbourne at Marvel Stadium, while his back-up Bailey Williams (hamstring) is also no certainty to play.
Defender Josh Rotham, who was used as a back-up ruckman in the pre-season loss to Adelaide, will miss the first month of the season with a broken arm.
Forward Jack Darling is recovering well from an ankle injury and is hoping to prove his fitness for round one.
If Naitanui and Williams are both ruled out, it will leave 22-year-old Callum Jamieson to go up against the might of North Melbourne big man Todd Goldstein.
Allen was successfully used as a pinch-hitting ruckman during the early years of his career.
But after missing all of last season with a foot injury - and with West Coast needing to fill the giant void in attack left by the retired Josh Kennedy - Allen is set to play exclusively as a forward.
"It is nice," Allen said.
"It's something we were working towards the last couple of years.
"Particularly earlier in my career, my versatility and ability to play in the ruck probably kept me in the side, because there were definitely days where Simmo and the coaching staff could have left me out and played another small forward (instead).
"But if the tap on the shoulder comes (to play in the ruck again), I'll definitely do it."
Allen, who booted 28 goals in 2021, said he is completely over his foot injury.
"I think that's why we had such a conservative route last year and that's why we took it the way we did with ruling myself out at probably the halfway mark of the season - just understanding how important it is to nip it in the bud and get it right," Allen said.
"If your feet don't work it's going to be hard to play footy, you can't run or do anything that's required.
"But it feels great, the body's been feeling really good for the last five or six months now and I've had a really good training phase."
Allen will shoulder a huge responsibility now that Kennedy has retired.
Kennedy, who booted 723 goals during his decorated career, has been keeping in touch with Allen to offer him advice.
"He was actually at training last week watching, so he gave me a couple of pointers, which is always nice," Allen said.
"He's terrific and has been a great leader and mentor for me in my time at the footy club.
"He's probably the reason I'm in the position I am today, because of the path he put me on when I got to the club."
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