Brooks was a concussion substitute for No. 3 Nkrumah Bonner, who copped a hit on the back of his helmet after unsuccessfully trying to evade a bouncer from allrounder Cameron Green early on day three.

After the mandatory medical checks and a change of helmet, Bonner batted for a further 40 minutes before retiring hurt. It was unclear at the time whether Bonner, who is reportedly feeling in good spirits, would be able to return.

By the lunch break it was becoming increasingly likely that Brooks would be substituted into the match and West Indies captain Kraigg Brathwaite implored him to be ready.

"There was a bit of deliberation on the situation," Brooks told reporters."The decision was made and I needed to get mentally ready and do the business for the team."

He had also spent the last couple of days being a willing reserve, which meant he didn't spend any time in the nets. "Last hit was on the first day of the game," Brooks said.

"I was just servicing the players. It's a batting day today, so I was just trying to get the other batters ready.

"I normally would have a hit. The other guys (batters) were having a hit... so I didn't get an opportunity to have a hit."

Brooks could have been on a hiding to nothing, but he had studied closely the grassy Optus Stadium pitch, while his previous experience at the Test level held him in good stead.

"I just basically played a lot of things in my mind that I saw in the last day and a half," Brooks, who has played 11 Tests with the last being against England in March, said. "I got myself ready and I've played at this level before."

He came to the crease late in the second session after the wicket of Jason Holder and equipped himself well with 33 runs off 58 balls. Brooks got through a menacing second new ball burst from quicks Mitchell Starc and Pat Cummins before falling to Green as West Indies got bowled out.

"It wasn't a rude awakening but a good start for me facing these guys," he said. "First time facing them in Australia. It's a very good surface and I enjoyed the challenge."

Brooks will likely get another chance to bat in West Indies' second innings, but he'll have to wait as Cummins resisted enforcing the follow on despite Australia boasting a massive lead of 315 runs.

With an Australian declaration looming on day four, Brooks said West Indies' batters needed to take heed of Brathwaite and debutant Tagenarine Chanderpaul's gritty approach, where they combined for a 78-run opening partnership.

"Four or five sessions," Brooks said when asked how long West Indies could realistically bat out for a draw. "That's what I think they will give us because I think it's still a good batting pitch. I don't think they will go too deep tomorrow.

"The openers showed a lot of fight. We still have a second innings to play."