Tasmania quick Jackson Bird was added to the Australia XI that delivered a much improved performance in the drawn third Test at Old Trafford when the tourists named a 12-man squad Wednesday for the Chester-le-Street Test.
With Australia 2-0 down with two to play, and so unable to regain the urn, there are those who argue now is the right time to give the twice-capped Bird his first taste of Ashes action.
But Clarke said Tests were too important for anyone to just be "given a go".
However, only once in a 14-Test career blighted by injuries has the 33-year-old played in three successive Tests -- and he broke down in the third of those matches, the 2010/11 Boxing Day clash against England, when he suffered an ankle injury.
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Clarke, though, said the fact Australia had little bowling to do on a rain-marred final day at Old Trafford would help Harris.
"In my mind I'm confident Ryano will be fine," Clarke said Thursday. "Us not bowling on that last day because of the rain is definitely going to help our bowlers.
As for the 26-year-old Bird's prospects of being selected for his first Test appearance since facing Sri Lanka at Sydney in January, Clarke said he would be treated like anyone else.
"I don't think anyone is here to 'give them a go'. That's not in any Test cricket and certainly not an Ashes series, especially the position we're sitting in now. It's about picking your best 11 players.