Green, 20, who has been likened to Andrew Flintoff, is tipped as an international star in the making if he can overcome the back problems which prevented him from bowling for much of the 2019-2020 season.
Playing as a specialist batsman, he scored three Sheffield Shield hundreds - joining Doug Walters as the only players to have three Shield centuries and two five-wicket hauls before the age of 21 - including a stand-out match double with undefeated scores of 87 and 121 against Queensland.
"Greeny is an incredible player and the scary thing is he didn't even bowl last year," Agar said. "For a young guy to come in and handle pressure situations as a standalone batter and make big hundreds and important contributions in big games showed mental ability well beyond his years in cricket. I can only see him getting better and better with the bat and then with the ball."
Alongside averaging 43.84 in his 15-match first-class career, Green has taken 28 wickets at 21.53 which included debut figures of 5 for 24 against Tasmania in 2017, figures he bettered against the same team in 2018 with 6 for 30 in a match haul of 9 for 42.
"When he's in full flight, Greeny can bowl over 140kph and swing the new-ball," Agar said. "He's two meters tall and to have someone like that in your team, who's got raw pace and can play as a specialist batter or a specialist bowler, that's some pretty scary talent.
"So, it's just about him getting his body right, keeping his mind strong for he's going to be under some pressure when people start talking about him. People already are and he's handling that really nicely so we're very proud of him here [at WA] and I think he's going to continue on a nice path."
Speaking in the first part of last season, shortly before the back injury was confirmed, Green played down the hype that had been building around him including when Ricky Ponting suggested he should be around the Test squad for experience.
"I think it's still way too early to be taking those comments pretty heavily," he said. "I've only played a couple of games as a batsman in the WA squad. I haven't really got those runs on the board, to be honest. I may have got a couple of good scores out of the way, but I'm definitely a good few years off I'd say."
Australia have long-searched for an allrounder to balance their Test side. Mitchell Marsh was recalled for the final Ashes Test last year and took 5 for 46 at The Oval before breaking his hand punching a dressing room wall in the early part of the summer which ruled him out of contention for the series against Pakistan and New Zealand. However, he returned to the ODI and T20I sides earlier this year and was awarded a CA central contract last momth.