Former Aussie quick Glenn McGrath has predicted Ryan Harris and Mitch Marsh will miss out on the Australia's XI to take on England in the opening Ashes Test in Cardiff.

McGrath expects the pace attack in Wales will consist of Mitchell Johnson, Josh Hazlewood and Mitchell Starc, while he's tipping Shane Watson to get the nod over fellow allrounder Marsh.

Leaving out Harris would be tough given he was a "quality player" but McGrath suggested he could be saved for the second Test at Lord's, where the right-armer took seven wickets in 2013.

"I'd be keen to play both Starc and Hazlewood in the first Test and you've got to play Mitchell Johnson," McGrath said.

"Ryan Harris hasn't played a great deal of cricket and they'll probably want to manage him throughout the series.

"So it might work out, there's always one guy fresh going into a Test."

Harris buoyed by performance against Kent

McGrath, speaking at a Hardys of Australia wine tasting function in central London, also backed Watson over Marsh.

"He (Watson) will get given the opportunity to start with and I want to see him go out there and perform - to really live up to the ability he has," McGrath said.

"If he comes into the first Test and performs, then it's his, if not then we'll wait and see."

The Test legend added England's attempt to unsettle Australia's batting linchpin Steve Smith with some pre-series sledging is unsurprising, but will have no impact on the star 26-year-old.

England quick Stuart Broad this week suggested England were licking their lips at the prospect of testing out Smith's technique at first drop in the upcoming Ashes series.

But McGrath thinks the England quick is simply "talking it up in the media".

"Being a bowler you can get away with it more than a batsman because it only takes one ball to prove you're right," he said.

Smith can't wait for his third Ashes series

"I had a bit of fun with that (and) maybe Broady is doing the same thing.

"You target the best batsman and get them thinking about a few different things rather than their own game.

"He's a bit unorthodox, his scoring options are different.

"But Smithy has shown in the past he's prepared to look ugly, to do it tough.

"Whether he bats three, four or whatever, I don't think it's going to make any difference."

McGrath says the first Test starting on July 8 would be crucial for Johnson after an "incredible" home Ashes series that left England's players with "a lot of scars".

On the flip side, McGrath said if England are to be competitive, quicks Jimmy Anderson and Stuart Broad will also need to hit their straps early.

"If Mitchell Johnson can get off to a good start here it will just reopen them and he will just power through."

Johnson confident after strong showing in tour match

Hazlewood is often compared to McGrath and on Monday the veteran backed the 24-year-old to excel in English conditions.

"I loved playing over here and loved playing with the Dukes cricket ball," McGrath said.

"I averaged two wickets a Test more with a Dukes ball.

"(So) I think he (Hazlewood) will enjoy that - he is the type of bowler that hits a deck and can swing the ball a bit.

"You've got to hit the seam in England to be effective, and he does."

McGrath said Hazlewood was "big enough and tough enough" to handle the pressure of playing an Ashes series in the UK.

Hazlewood on his first Test chances

McGrath, famous for predicting Australian clean sweeps at the Ashes, duly delivered on that front again.

"Considering Australia won 5-0 last time in Australia, I'm just continuing that, so my prediction is Australia will win 10-0 (on aggregate)."

Glenn McGrath will be writing exclusively for cricket.com.au throughout the #Ashes