Cowan said he is confused by Australia's selection policy after being dropped from NSW's Sheffield Shield team for a younger teammate, while veteran Shaun Marsh earned another recall to the Test side.

The 35-year-old was dropped for the first three shield rounds to give rising star Daniel Hughes a chance to press for national selection. Cowan is now back in the Blues squad for the shield match against Victoria at North Sydney Oval starting on Friday.

"The only sour element comes from the fact that three weeks ago I was evidently too old, then someone [Marsh] who I played youth cricket with gets picked in the Test team," said Cowan.

Marsh, 34, will bat at No. 6 against England after being recalled to the Test team for the eighth time.

"Selecting the country - whichever way you want to select it - it needs to be consistent and those goalposts around performance need to be set in stone," said Cowan. "The policy of the young guys playing I've got no problem with, as long as it's a selection policy that sticks."

The 18-Test batsman said the change in selection policy was "pretty hard to take".

"I feel for those guys who are pushing for Test selection and they probably don't know what is required," he said. "We just want a little bit more consistency and clarity around selection."

Cowan said even Australian captain Steve Smith was surprised at Marsh and wicketkeeper Tim Paine's inclusion in the Ashes squad instead of younger players.

"He [Smith] certainly had a view that that's the way selections would go and I think the selection panel as directed by [high performance manager] Pat Howard turned that on its head," he said.

"Who knows what they're thinking for the future?"

However, the veteran heaped praise on Marsh, Paine and Ashes debutant Cameron Bancroft.

"I think the Australian cricket team is in a great place to return the Ashes."

NSW sit on top of the Sheffield Shield table after an unbeaten start to the season.