Australia captain Michael Clarke believes it is only a matter of time before Shane Watson makes some big hundreds for Australia.

The long wait between Watson's second Test century and his third dragged on ever further on Thursday when the 31-year-old was dismissed for 83 as Australia continued to dominate the Boxing Day Test against Sri Lanka.

That now means Watson's 38-Test career has delivered an impressive 19 fifties, but just the two hundreds as one of Australia's finest batsmen continues to fall short when in sight of triple figures.

But Clarke is not concerned about Watson's inability to go on and post a hundred and thinks his vice-captain will deliver a big score sooner rather than later if he can continue his current vein of form.

"There has been a lot of talk about Watto's statistics in regard to hundreds scored, and he has certainly spoken openly about that," Clarke said.

"For me it is about Watto playing his best cricket and I am confident that if he is doing that he will make big hundreds.

"I have seen that in one-day cricket and I have seen that a couple of times in Test cricket.

"If he continues to play the way he played today and shows that patience and that discipline I have no doubt at all that he will score plenty of hundreds for Australia."

Clarke also found himself having to defend Watson for the shot that saw him dismissed.

Watson had played few false shots all day, but pulled a short delivery from Dhammika Prasad straight down the throat of Thilan Samaraweera at deep square-leg.

"He (Watson) showed a lot of discipline in his shot selection and even the ball he got out on, as his captain, I am not disappointed with, Clarke said.

"He pulls and hooks as good as anybody in our team, so it is a shot that he generally plays really well.

"Nine times out of 10 that will go for four or six.

"It is just unfortunate for him that today it went straight to the fielder."

Clarke's 106 on Thursday helped Australia into a near match-winning position at stumps on the second day of the Test, with the hosts ending the day at 8-440 and with an overall lead of 284.

And not only did the Australian skipper score his maiden Test century against an at times listless Sri Lankan attack, but he also broke Ricky Ponting's record from 2005 of the most Test runs scored by an Australian in a calendar year.

Mention of either achievement drew a smile from Clarke after the match as he reflected on what it meant to him to reach triple figures at the MCG and to surpass Ponting's mark of 1544 runs in a calendar year on the same day.

"It is nice to get that monkey off my back and get my first hundred here... and in my eyes he (Ponting) was certainly the best player I played with, so to beat any record Ricky holds is very special," Clarke said.

Clarke said he has no plans on declaring Australia's first innings just yet and that he would love to bat on further on the third day so Mitchell Johnson (73 not out) can make another hundred.

"As many runs as we can possibly get tomorrow would be handy," Clarke said.