Johnson's return to the Test side after a 12-month absence proved to be short-lived, despite him impressing in the third Test loss to South Africa by taking six wickets. Starc, eight years younger than Johnson and making his first Test appearance since April, claimed six wickets in the second innings of that match which was enough to get him the nod for Hobart.
"Obviously it's a tough selection trying to cut 12 down to 11, especially with the way that Mitchell Johnson performed in Perth," Clarke said. "Mitch (Johnson) would feel unlucky there's no doubt about that. Mitchell Starc has been in the queue for a while now and I thought he came in and did a really good job in Perth as well."
He added: "We've gone for this attack for this Test match in these conditions against the opposition we are playing."
Clarke denied that there was a need to play Starc to build up his experience and confidence for the upcoming tours of India and England.
"For me, I'm not looking at the Ashes at all. The reason Mitchell Starc is there is that he's been next in line in the queue for a while. He's performed really well in the shorter form of the game for Australia," Clarke said.
"He got one Test in Perth, got a six-for and got 70 odd with the bat as well, so it's not a bad start. At the end of the day, you have to do what's best for the Australian team. You have to pick the best XI players to help you win a Test match."
Clarke backed Johnson to bounce back from the setback, and thinks that he will take it as a sign of the depth of the Australian bowling attack rather than an indication he is not up to scratch.
"It was a tough selection to leave Mitchell Johnson out, as it would have been whoever we left out, but I've been saying that it's a nice problem to have to have 12 blokes who want to play and have performed well," he said.
"Mitch will be fine and continue to work his backside off and wait for another opportunity and when that comes grab it with both hands."