Time in the middle is one of cricket's oldest adages.

It is something Australia has struggled with on overseas tours in recent times. The value of time in the middle in the warm-up match against Pakistan A in Dubai will reveal itself in the first Test starting on Sunday.

But Australia's batting performance in its only innings ahead of the series was telling. Not one, but three Australian batsmen, Mitchell Marsh, Shaun Marsh and Travis Head, faced more than 200 balls in the innings.

It is telling in that no Australian batsman has faced 200 balls or more in an innings any warm-up match in the last six overseas test tours dating back to 2015. Six times Australian players scored hundreds but were retired well before the 200-ball mark.

Welcome to the Justin Langer era. Where hundreds weigh heavily in selection and batting for long periods is an expected minimum.

Australian captain Tim Paine revealed ahead of the tour that Langer had told his batsmen to leave "their egos at home and be prepared to bat for a long, long time".

When Mitchell Marsh reached his century against Pakistan A on day three there was no thought of retiring him to give others a chance. He went on to make 162 from 298 balls, the longest innings of his entire first-class career.

"My game plan today was to be really patient and play every ball on its merits and if it took me the whole day to get my hundred, so be it," Marsh said at the close of day three. "It was really nice to spend that time in the middle."

Shaun Marsh faced 230 balls for his 94 while Travis Head remained unbeaten on 90 from 200 balls when Australia declared overnight on day three.

Time in the middle could factor in Australia's selection for the first Test. Matthew Renshaw was predicted to be a lock-in at the top of the order, given he is one of just three specialist batsmen in the touring party with previous Test match experience. But Renshaw did not bat in the practice match after he was struck on the head while fielding at short leg. He was substituted out of the game as a precaution but was running laps on day four.

Langer revealed that he expects Renshaw to be fit to play but that might not be enough for him to be selected. "I think Matthew Renshaw will be physically fine," he said. "The problem he's got is that he hasn't played much cricket. He went to the Australian A tour [of India] and got a hamstring strain and missed a fair bit of cricket on the Australian A tour. He's come here and hasn't played. He played the second Australia A game and didn't spend much time in the middle."

Renshaw made 0 and 19 and faced a total of 45 balls in the second unofficial Test against India A in Bengaluru in early September. He played two matches for Australia A in limited-overs tri-series in India in August. That is the only cricket he has played since his prolific stint with Somerset was cut short in June due to a broken finger.

Langer said 24-year-old Queenslander Marnus Labuschagne was firmly in the frame to make his debut after making 39 not out from 73 balls against Pakistan A.

"In the history of Australian cricket a lot of people take their opportunity through injury and I thought Marnus fielded brilliantly, looked really good with the bat yesterday, bowled a few overs of leggies, so he's certainly put a strong case forward for selection as well," Langer said.

There is no doubt Head and Aaron Finch will make their Test debuts on Sunday with Langer saying both men deserved their baggy green caps.

Finch didn't spend the hours at the crease that Head did, but hit 54 from 91 balls opening the batting for the first time in a four-day game for Australia. He has batted predominately in the middle order for Victoria in Sheffield Shield cricket. Finch spoke of adapting his game from his trademark limited-overs aggression.

"It's still about playing my natural game," Finch said on day two. "There will be an opportunity to taper that slightly with the conditions and with the wicket.

"You have to pick your moments and pick your bowlers, pick your balls and just to do it for as long as you can."

Australian egos have been under the microscope over the last six months, but early evidence suggests they have heeded Langer's advice ahead of their first Test assignment under his stewardship.