The first overall selection in the NAB AFL Rookie Draft only played Australian football for the first time this year with the Reynella Wineflies in South Australia.

Nine months later, towering 203cm ruckman Sam Draper is a Bomber.

"I can't believe it," Draper told 5AA radio on Monday.

"I kind of got told it's not looking likely it's going to happen this year, so I wasn't expecting too much leading up to it.

"If I did (get drafted), it would be a bonus.

"(Essendon) called me up earlier today to let me know they were going to pick me at pick No.1.

"Honestly I can't believe it, it was so hard to sink in."

Draper was a centre-back in soccer until last year before he joined the Wineflies in February.

South Adelaide came knocking two months later, and it didn't take long before he began to come on to the radar of AFL clubs. 

"It's my first year of footy this year so it was pretty hard at first, just getting to know the game," Draper said.

"By the end of the season I really started to find some form and I was improving each game. 

"I've grown this year so hopefully I've got more left in me." 

Essendon list and recruiting manager Adrian Dodoro said Draper would take time to develop. 

"We desperately needed to find a developing tall, they’re so hard to find, there are not many around in AFL circles at the moment," Dodoro said. 

"He only started playing football in February this year. He’s had a pretty steep rise this year. 

"He’s a big lump of a kid, he’s quick, has got good agility and is a former soccer player."