As he sat back in the team bus from Colombo to Galle, the Australian captain Michael Clarke had plenty of selection questions to contemplate. The shape of his bowling attack will likely be defined by the state of the pitch for the first Test, but it is a little more difficult to weigh up the merits of his two candidates for No. 6 batsman.

On the strength of a strikingly composed 101 retired in the Colombo tour match, Usman Khawaja has made arguably the more convincing case. Though he opened the batting, Khawaja stayed long enough to see the wicket wear and the spinners wheel away, showing he had developed a more convincing method against spin than the one that saw him defeated by Graeme Swann on debut in the fifth Ashes Test at the SCG in January.

Yet Shaun Marsh's hold on the No. 6 berth has appeared much the stronger in the weeks leading up to the match. He was not taken on the Australia A tour of Zimbabwe, where Khawaja failed to make a score of note in four innings, because he was deemed almost an automatic selection for the tour of Sri Lanka. Marsh has also seen far more of the Sri Lankan Test attack than Khawaja, and has the game to dominate an attack, whereas Khawaja is more likely to accumulate with a game best suited for the top four. Should the merit of one silken innings in a tour match overrule earlier conclusions?

"I don't know, I'm not sure. [Khawaja is] another one who grabbed a hold of his opportunity and that's all you can do," Clarke said. "Obviously he hasn't made too many runs leading into this three-day game in the Australia A set-up, in county cricket and the back-end of NSW.

"He's another one who has put his hand up and said `give me a chance'. I also thought SOS [Marsh] did well in that first one-dayer he played, when he made 70 and creamed them. He played the spin really well. We've got to have a real good think about the position.

"Usman's opened the batting here and he played his Test at number three for Punter [Ricky Ponting], but in saying that what more can you do? It doesn't matter where you bat, you get an opportunity and try and make a big score and that's exactly what he's done. It's going to be an interesting couple of days."

Once he has finished thinking that over, Clarke can devote a unit of time to his own batting, which has appeared nicely grooved so far on tour. That groove is a new one, for it is 10 Test matches and more than a year since Clarke last passed three-figures for his country. It is a streak that has coincided with his move from No. 5 to No. 4 in the batting order, a change that is minor in number but major in intent.

At No. 5 Clarke was reacting to the agenda set by either his top order colleagues or the opposition's bowlers. A place further up and he is setting that agenda himself. It is a task he is yet to adapt to.

"My preparation's been good. I'm hitting the ball well," Clarke said. "It means nothing to be honest going into the first Test apart from getting the confidence in my mind that I know I'm batting well. Starting your innings in these conditions is as hard as anywhere in the world.

"Generally batting four I'd imagine I'll be coming in facing spin early with a couple of bat pads, a slip and things like that so I've got to stick to my plan. That's what I've tried to do in the one-dayers and this game here - back the way I've been training, back the way I feel I play my best against spin and it's worked so far. Things could change for the first Test.

"I really want my momentum to go on and I'm really keen to make sure I'm building it. I couldn't ask for better preparation but it doesn't guarantee you too much unfortunately, I wish it did."

As for the barren run of Tests without a century, Clarke is concerned less with numbers than he is with making sure that his batting has the presence required of an Australian captain. His predecessor Ricky Ponting stood as a most outstanding example of that presence, until the burdens of captaincy dragged his batting down.

"I don't really think too much about that. I know I haven't really performed as well as I'd like to. I had a poor summer against England," Clarke said. "I know I need to be leading from the front, put it that way, especially now that I'm captain.

"My form hasn't been as good as I would like in Test cricket. I've always said Test cricket is the ultimate to me, the pinnacle, and I want to be at my best. I couldn't ask for better preparation but now I've got to do it when it counts."

The bus trip from Colombo to Galle takes around two hours. It may not be a long enough journey to accommodate all that Clarke must ponder.

Daniel Brettig is an assistant editor at ESPNcricinfo