Michael Clarke says first-class system is the key to Australia's success

MICHAEL Clarke has cautioned administrators to be careful making changes to Test and Sheffield Shield cricket.

Speaking in Perth before tonight's one-day match against Pakistan, the Australia vice-captain was wary of the push for day-night Test cricket and questioned the quality of the balls that may be used.

He also warned that any expansion of the highly popular Twenty20 Big Bash should not come at the expense of Sheffield Shield cricket, which allows Australia to produce ready-made international players. That has been obvious this summer, first with the impressive emergence of Doug Bollinger as a frontline fast bowler and more recently the instant success of seamers Clint McKay and Ryan Harris.

With four of Australia's five Ashes squad fast bowlers injured at times this summer, all the replacements have grabbed their chances, with Harris coming in for Tuesday's match in Adelaide and claiming the man-of-the-match award with five wickets.

He replaced the injured Peter Siddle, who showed no signs of his back problem during training at the WACA Ground yesterday but will be assessed again this morning. If Siddle is fit, it will create a logjam of fast bowlers, with Mitchell Johnson coming back after a break to play his first one-day match of the summer in place of the resting Bollinger.

Clarke expects either wicketkeeper Brad Haddin to be promoted or all-rounder James Hopes to slot in as opening batsman, in place of the resting Shane Watson.

Clarke said that Australia had so much flexibility because of its domestic cricket.

"The strength of Australian cricket since I've played the game for either NSW or Australia has been the first-class system," Clarke said.

"For me the priority is to make sure we don't touch that or we don't lose anything from that. If things are altered or improved that's fantastic, but the first-class system we have is fantastic and that's why we are so strong in all three forms of the game.

"There's guys pushing hard in the one-day domestic competition to be at the top of the list with both bat and ball to get an opportunity if guys are rested or injured.

"That's the way it's always been since I've played international cricket, there's always someone up your backside wanting to take your spot. I don't think Australian cricket can be in a better position if you've got that happening."

Clarke was also keen to see what type of ball would be used for proposed day-night Test cricket.

Trials will begin next week in state second-XI matches with pink and white balls but there are ongoing concerns about both balls being able to retain their colour for anything like the 80 overs required in Test cricket before a new ball can be taken.

"I would like to see the ball first, and where are we going to play the day-night Test matches?" Clarke asked. "Batting under lights in one-day cricket is much harder than batting during the day.

"Conditions will dictate that, and they will have to try the day night games in first-class cricket before Test cricket.

"I am interested to see how it pans out. If it can work it would be great for the game.

"The public would certainly find it easier for the games played during the week to come out and watch after work."