"He'll start bowling around three months post-surgery, but I want him to take it quietly for the first month," Young told Australian Broadcasting Corp. Radio.
"(He won't be) fully fit at international level for four to five months."
"I was pleasantly surprised. He's a 32-year-old who's been playing international cricket for 12 years," Young said.
"I thought there would be a fair bit of wear and tear on the shoulder. We didn't find that, we found a lesion and that in turn was pressing on a nerve and starting to weaken the muscle and that was our real concern."
Muralitharan has 532 wickets, five more than Australia leg spinner Shane Warne.
The 34-year-old Warne had drawn level with the Sri Lankan on 527 last month when Australia hosted Sri Lanka in a two-Test series.
Muralitharan told reporters last week in Melbourne he thought Warne was a wonderful bowler and fully deserved the title of world record holder.
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Australia will then host two Tests against New Zealand and three against Pakistan.
Muralitharan pulled out of the second and final Test against South Africa which started in Colombo last week and is set to miss the ICC Champions Trophy one-day tournament in England next month and Sri Lanka's tour of New Zealand in December.
Muralitharan, who has previously been called for throwing during tours of Australia but has since had his action cleared by officials, has taken his wickets in 91 Tests.
Warne has taken 112 matches to reach his total.