Australia face a fast-bowling selection dilemma for the Ashes, says coach Darren Lehmann.
Left-armers Mitchell Johnson and Mitchell Starc are competing with right-arm seamers Ryan Harris, Josh Hazlewood and Peter Siddle for just three spots in the side.
Australia fly to England on Wednesday, with the first Test on 8 July.
"Those guys have given us a massive headache - albeit a good one," said Lehmann.
"Two of those five guys are going to be unbelievably unlucky to miss out, but that's what happens when you're playing good cricket.
"You have to make those hard decisions."
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Johnson, 33, terrorised England's batsmen in his side's 5-0 series win over England in 2013-14 with 37 victims, while Harris, 35, took 22 wickets as he shared the new ball.
Siddle has taken 67 wickets in 20 Tests against England, but appears to have fallen down the pecking order following the emergence of Starc and Hazlewood.
Tall quick Hazlewood, 24, was named man of the series against West Indies after picking up 12 scalps at an average of 8.83 in two matches while Starc, 25, took eight wickets in the Caribbean and was one of the stars of the recent World Cup which Australia won on home soil.
Before the opening Test in Cardiff, Australia face Kent and Essex in warm-up matches, and Lehmann says those fixtures will help define his selection for the Ashes.
"We need to see how the bowlers pull up and how they bowl in the different conditions, on different pitches and with the different ball," he added.
"It's been two years since our last Ashes tour and there's a big change in mindset for me personally and the team compared to when we were there in 2013.
"The guys are definitely in a better space than they were two years ago. We're really close as a team and we know what we we've got to do on and off the ground to achieve our goals."