The simplistic answer is they're both ruckmen burning with basketball talent.
Brogan won an NBL championship before his AFL premiership with Port Adelaide, while Downie represented Australia in the under-17 world championships in 2010 and was drafted by GWS a year later.
The more genuine reason for Brogan's enthusiasm is he's watched closely how hard Downie has had to work to earn his maiden AFL match.
"Tom Downie has been one of our most improved players on the list," Brogan said of the 20-year-old who will tackle Fremantle in Perth on the weekend.
"A year ago - jeez he was really battling. It was no fault of his own, he was just new to the game and he was a long way back. But he's closed that gap pretty well.
"He's a good kid, he wants to learn. He's got so many attributes - he can run, jump and reads the game really well."
Downie was named as the Giants' starting ruckman on Thursday night, knocking down the door with some stellar form in the seconds.
"He's been one of our best players in the NEAFL every week. He's been dominating," Brogan said.
"Like anything, he's just going to take a bit of time. But he's got the right attitude."
Andrew Phillips, GWS's other hope of support for Jon Giles next year, was booked in for hip surgery this week after failing to play a game in an injury-cursed second season.
"He showed so much promise last year," Brogan said of Phillips, who came off the rookie list in 2012 to play nine games.
"He's got a real x-factor about him. It's been disappointing we haven't been able to get him going this season, but long term it's important we get his body right."