Alex Malcolm is an Associate Editor at ESPNcricinfo
Green, 22, turned the game on the third evening with a blistering spell to spark a massive collapse after England had reached 0 for 68 chasing 271 to win.
Green took three wickets in a six-over burst either side of the evening break. His extra pace forced Rory Burns to chop on to halt England's momentum. He hit Dawid Malan flush on the helmet with 138kph/86mph bumper that rocked England's No. 3.
Malan, having already survived a couple of near chop-ons and several plays and misses, then dragged another back-of-a-length ball on to his stumps, before Green found Zak Crawley's outside edge with some late away movement to leave England reeling. They lost 10 for 56 to lose by 146 runs and hand Australia a 4-0 series triumph.
Coming on the back of his critical 74 with the bat in the first innings, Cummins was in awe of Green's ability.
"He's just as good as any allrounder in the world at the moment I think," Cummins said. "For someone so young, as a captain, I feel really lucky not only to draw on him as a bowler but when he's next into bat I just feel so calm.
"He showed he absolutely belongs at this level is a Test batter and then as a bowler, he's a genuine fourth quick.
"I feel like I turned to him sometimes before I turned to myself or someone else. He's just got that bounce, he's got the control, incredible skills, and he's been so bowling so well, we've only had to bowl him 10 or 15 overs a day or an innings. Again, you forget how young he is, just seeing him at gully as well.
"He is absolutely the complete package. But he's young, so we've got to keep looking after him. But a bright future ahead."
Green finished the series with 273 runs at 32.57 including two half-centuries, and 13 wickets at 15.76, emphatically silencing any doubt about his place in Australia's Test side.
"He had so much leeway, not only because of his bowling but he's scored a lot of runs in Shield cricket consistently over the last couple of years," Cummins said.
"He's played some big innings. Internally we weren't worried at all about how he was going. I think in himself being so young, I think he needed to grow and believe and I think you saw that last week particularly."
Cummins himself grew into the Test captaincy across the series. Any queries on how the leadership would affect his bowling were quashed as he finished the series as the leading wicket-taker on both sides despite only playing four Tests with 21 scalps at 18.04, bookended by a five-wicket haul in the first innings of the series and seven wickets in the final Test in Hobart.
"That was probably my biggest worry in accepting the role as captain," Cummins said.
"I'm in the team as a bowler. I want to make sure that's protected and I'm able to perform as well as I'd like. I think with each game I felt better at managing that. I could really switch off, take off the captain's hat and just be a bowler for my overs.
"Even little things around bowling changes, moving fields in between my overs I felt like I got better at managing that as the series went on and so that's a hugely pleasing thing. Again, it might be difficult in the heat or longer innings, but I feel like it's something I'm only going to get better at."