Australia seek sweet success in Kandy

A stunning maiden Test century from Kusal Mendis and a hamstring injury to Stephen O'Keefe are weighing heavily on Australia after relinquishing their dominant position to Sri Lanka in the first Test in Kandy.

At tea on Thursday's third day, Sri Lanka are 5-253 in their second innings, 167 runs ahead in a formidable fightback after being blasted out on day one for just 117.

They have a diminutive 21-year-old in only his seventh Test to thank.

Quick single: Smith sends himself into a spin

With his side's hopes hanging by a thread when he walked out at No.4 and Sri Lanka 2-6 - still 80 runs behind Australia - his timing in scoring his first Test ton was impeccable.

Mendis took on the Australian bowlers from the outset, cutting and driving the fast bowlers and sweeping the spinners with good effect in a brilliant 157 not out.

He almost single-handedly hauled Sri Lanka back into the contest, especially in his 117-run union with Dinesh Chandimal (42).

His score is easily the highest score of the match with the next best being Adam Voges' 47 in Australia's total of 203.

It surpassed Mendis' previous best of 53 at Test level and was an enthralling dig against the No.1-ranked Australia considering he'd only scored one first-class century previously.

Aside from trying to find a way to extract Mendis, Australia have another major concern.

Left-arm spinner O'Keefe left the field with a right hamstring complaint midway through the session.

Cricket Australia says it is assessing the injury, but it will be a big blow to the tourists if he's ruled out for the rest of the innings, given the wicket is taking plenty of turn and O'Keefe (1-42) had been creating a number of chances.

Quick single: Sri Lanka mystery trumps Aussie planning

Mendis' aggression was in contrast to his fallen teammates who had poked and prodded on a pitch with a bit of inconsistent bounce and plenty of spin.

Of the 15 Sri Lankan wickets to fall so far, eight have been lbw.

It started in the opening over of the day with Mitchell Starc - bowling at good pace in high humidity at Pallekele Stadium - caught Dimuth Karunaratne on his crease playing around a full ball.

The batsman failed to have the lbw decision overturned on review.

Mendis and skipper Angelo Mathews had earlier consolidated before Nathan Lyon stepped in to end their 41-run partnership.

Mathews went forward tentatively and was caught at bat-pad by Joe Burns for just nine.

It hasn't been a great game for the captain who needed to lead the way in a youthful team - he made 15 in the first innings, bowled three overs and didn't use the DRS judiciously.