Not having played Test cricket since November because of an elbow operation, the selectors went with the young pacemen who won Australia the series in South Africa - Mitchell Johnson, Siddle and Ben Hilfenhaus.
However, Johnson has had a difficult tour and struggled again Sunday. His Test place must now be on the line after his seven-over spell conceded 42 runs - a run a ball.
'I wasn't given any guarantee I was going to play,' Clark said of a possible Test return.
'The selectors had an idea and they went with that idea.'
'I thought I was a real chance (to play the second Test at Lord's) but given the boys played really well in Cardiff, and all the bowlers did really well, it was always going to be hard to change that team.'