Compton opened for England in nine consecutive Tests and hit back-to-back centuries on the tour of New Zealand. But he was axed after struggling for fluency in the return series against the Black Caps and will not be on duty at Trent Bridge, with Joe Root promoted as Alastair Cook's new partner.
Australia skipper Clarke said: "We haven't bowled to Joe yet but we didn't manage to get Nick out that easily, so I'm happy he's not playing to be honest.
"Nick has showed in the last couple of four-day matches he has a very good defence and I'm surprised he's not in the team for the first Test."
England captain Cook was adamant that Root deserves his selection ahead of Compton in the line-up for the first Test.
"Joe has handled himself in every situation fantastically well," Cook said. "He has managed to change his style to every situation and is a fantastic young player."
Both captains said they knew their starting XIs but did not give any clues.
The pitch is expected to be dry and the weather conditions warm which might give the batsmen an advantage at a ground where swing bowlers usually perform well.
But Cook, leading England for the first time in an Ashes series, played down the significance of winning the toss.
"The toss is important but how you play is more important," he said. "Our group of bowlers have the skills and experience to hold us in good stead in any conditions."
Cook said the England players had been inspired by a weekend spent watching the British and Irish Lions win their rugby test series in Australia and Andy Murray's momentous victory at Wimbledon.
"That was an incredible moment for British sport," Cook said. "A lot of our players are big tennis and rugby fans and it was fantastic watching as genuine sports fans."
Clarke said with a wry smile that he was aware of the recent British sporting success but was confident his inexperienced team were capable of winning back the Ashes.
"Every one of the boys has prepared to the best of their ability," he said. "I've told them to play with freedom, to back their ability and play their natural game.
"Our preparation is done. Now it's about what we do on the field."
Clarke was more than happy to accept his team were underdogs going into the start of the five-match series on Wednesday while Cook was confident his side would handle the pressure of being favourites.
"We have been favourites in other series as well and I think it sits well," Cook told a packed news conference in the pavilion. "But cricket is not played on paper and it is all about delivering on the pitch.
"Australia are a very, very good side. They have some world-class players and I think there is going to be a very good standard of cricket in this series.
"We've always known it's going to be one hell of a battle," said Cook.
Australia's preparations have been far from ideal, with Darren Lehmann brought in as coach to replace the sacked Mickey Arthur just over two weeks ago.
"We come here as underdogs but that won't affect our performances," Clarke said. "Darren and Mickey are two completely different people.
"Personally I have enjoyed talking cricket with 'Boof' (Lehmann) who I was lucky enough to play with. We are all embracing Darren's style now."
Cook said the England players could not wait to begin their defence of the Ashes.
"Everyone is desperately excited to be here today after such a long build-up," he said. "There are a lot of nerves and excitement but it's important not to blow it out of all proportion."