"For me, she's the best athlete on the tour, she's an Olympic sprinter with a racket in her hand," Macci said in comments to OLBG, a sports betting community.
"I would love to work with Coco Gauff. I think I could rewire her entire forehand if she and her team wanted to. I'd teach her the ATP forehand," the 68-year-old said.
"Mentally, she has it. Her backhand is money, and her volley is great. The serve, I would rewire slightly, it's loose, it's big, it's free, but it isn't quite as good as it could be.
"She's still so young, but the muscle memory has been there for so long on the forehand. If she took a bit of time out and modified that, she would have so much ability.
"I'd create a completely new stroke for her, and it would fully change her career. It could go from her weakest shot to her best shot."
As Gauff decides whether or not to take Macci up on his offer, one thing she may consider - his resume also includes coaching her Wimbledon conqueror Kenin.