Australia is counting on their ironman Nathan Lyon to break through the fatigue barrier and on day five to a fourth innings win in Galle.
Lyon sent down 35 overs on Sunday, while Sri Lanka on day three went 6-431 and led by 67 over Australia in its first innings.
But the visitors are adamant that all hope is not lost in Galle, and see the opportunity to narrow Sri Lanka’s lead to around 100 and force them to bat last on the final day.
For that plan to succeed, much of the responsibility will lie with Lyon.
The offspinner has already sent 56 overs for the game, and is almost certain to surpass his own biggest workload of 57.2 overs in one turn on Monday.
He also battled cramps late in the day and drank pickle juice as he tried to battle through Galle’s humidity with his numbers of 2-160.
But with the field expected to deteriorate, Australia will be counting on him to perform.
“We’re comfortable with where he is physically and the job he can do,” McDonald said.
“There’s nothing to indicate he’s tiring or getting older or anything like that. I think he’s bowling as good as ever.
“We saw that last week (when he took nine before the game) and we see it again today.
“Changing his angle of attack is something he probably hasn’t done much in his career. I thought he was quite dynamic in the way he did it today.
“And every time he faces a challenge, he finds a different way to do it. I think it’s an improvement from last time.”
Mitchell Swepson will also play a vital role, probably throwing better in the second Test on a harder wicket for figures of 2-90 than he did in the first.
But first Australia must break through Sri Lanka early on Monday and then hit well to give themselves something to bowl against.
Australia has only once cleared a deficit of more than 25 in the first inning to win in Asia, in 2006 against a side of the minnow in Bangladesh.
“Right now we are lagging behind, that’s our problem, we have to work through that,” McDonald said.
“Tomorrow is another chance in the morning session to get that number eight batter in Mendis, and we think they have a long tail.
“(If we can) keep that lead at about 100 and we’re good and real in this game with a fantastic hitting unit that can still do their job on what’s still a very real surface.”