Siddle has the chance to reignite his Test career after being selected for next month's two-match series against Pakistan in the UAE.

The 33-year-old will form an important part of the pace attack alongside Mitchell Starc, with the duo set to shoulder a big responsibility in the absence of Pat Cummins and Josh Hazlewood.

Siddle's Test career looked dead and buried after he re-injured his back in a 177-run Test loss to South African in Perth two years ago.

The 187cm paceman claimed just three wickets in that match, with his speed dropping as he battled back pain.

The injury continued to plague Siddle in 2017 but he's bounced back strongly in the past year, with his recent hot form for English county side Essex earning him a Test recall.

Langer was appointed Australia coach in May and he was keen to let Siddle know he remained in the Test thinking.

"He sent one message saying, 'Just remember that every game counts'," Siddle said.

"That was the best little message I had from him. I didn't have to ask any more. I knew what he meant.

"That's how I was approaching my cricket anyway. But to hear it from him, it was good backing."

Langer's 15-man Test squad features five uncapped players.

Aaron Finch is a strong chance to open the batting, while Travis Head, Brendan Doggett, Marnus Labuschagne and Michael Neser are the other new players looking to press their case.

Glenn Maxwell was a surprise omission and Siddle hopes it won't be long before his Victorian teammate is in the Test side again.

"Coming home and being around him (on Monday), he was a little bit confident he was going to be part of the squad," Siddle said.

"I do feel for him. I know he'll be shattered but I know he'll go out and work hard and push his claims for the summer."

Australia face an uphill battle to beat Pakistan without banned trio Steve Smith, David Warner and Cameron Bancroft.

The loss of pace duo Hazlewood and Cummins to injury further depletes the weakened side.

Langer is making no promises about what fans can expect.

"How do you replace Steve Smith? He's like almost Bradmanesque the way he's played the last few years," Langer said.

"So it's hard to replace him, as it is with David Warner, who is a run machine.

"Losing those two is a hammer blow but it is what it is."

Australian Associated Press