An elegant left-hander, Marsh, will be available for Glamorgan in all three formats of the game and will be available for the full county season subject to the 2018 IPL draft, whereby if Shaun is bought for the IPL he will join the Welsh county following his IPL commitments.
Warner was unable to bat in the nets for as second-straight day, only facing a free throw-downs before exiting the field for treatment. After being criticised for his inclusion in the Ashes squad, the southpaw, who was expected to start the opener against England at the Gabba might miss out as he is reportedly suffering a back problem.
Marsh's experience makes him a road-tested option and he will blend will with Glamorgan's exciting new crop of homegrown products.
"My neck is quite stiff, but I don't think a sore neck's going to keep me out", Warner said.
"He's just had a hit. he's very confident, and he says he's good to go".
Marsh has a history of back trouble and was restricted by a jarred back in his most-recent Test earlier this year in India.
"We wanted to bring in someone who is experienced at global level, can bat at the top of the order and can play in all three formats of the game, and Shaun ticks all of those boxes for us".
He said: "It's disappointing for the England team and the country. We'll still prepare the same and be absolutely ready for him to play".
But the opening batsman was confident of taking the field when he addressed the press on Tuesday, revealing the medical attention was only precautionary. "It's quite sore. I haven't really had a stiff neck like this one".