Sayer, who tore her ACL last May, is back in a Matildas camp, one month after returning from injury with Swedish club Kristianstads.
Fowler, 22, was injured while playing for Manchester City last month and will be in a race against time to feature in next March's Asian Cup.
"As soon as I heard Mary's news, I did reach out to her, because we are around the same age," Sayer said.
"We've grown up, we've played together in the youth teams as well.
"I just reached out, said sorry for the news and offered if she needed any help at all, especially because I had to do a lot of research in the type of graft that I had to do in my knee.
"But she's got a really good crew around her and really good resources at Manchester City, and she's very, very strong physically and mentally already, so I think she's really got it in the bag.
"But if she ever feels like she needs to reach out, I would be more than happy to offer anything that I've learned."
Sayer, 23, knows as well as anyone the hard rehabilitation road Fowler is facing.
"It was definitely the hardest thing I've ever done in my life," she said.
"Lots of ups and downs, but it's really showed how much I can just hunker down and be single-mindedly focused on one task.
"I was in the gym like four-plus hours a day, twice a day, and I think that's what has helped me come back so quickly.
"I came back 11 months after my surgery."
Sayer has scored two goals for club since her return and feels a more "well-rounded" player coming into Matildas camp.
"The knee is never going to be the same, especially being cut open in six or more places," she said.
"But I think I've done the best that I can, and it feels really great at the moment.
"I've come back even stronger, I think, and more motivated than ever."
Sayer had aimed for the June window but after her "incredible" surprise call-up, is ready to pick up where she left off against Argentina.
"It was a surprise, for sure, because I've only been playing back for about a month. I've only just hit my limited 90 minutes on the weekend," she said.
"But any call up for the national team is incredible, and I'm so grateful to be here."
