Buller, who was taken with the 15th and final pick a fortnight ago, is a powering 199cm key forward, who showcased excellent form for Claremont in the WAFL, including a towering four-goal, 22-disposal and 14-mark display in a victory over South Fremantle earlier this season.
The 22-year-old was overlooked in the 2019 draft, having played alongside former Melbourne premiership ruckman and now Fremantle Docker Luke Jackson, Trent Rivers, and now teammate Chad Warner in Western Australia's Under 18 Championship.
He wasted little time carrying on his goalkicking ways, booting 5.4 in Sydney reserves' narrow four-point win over Sandringham last Friday.
Arnold, a versatile big man taken fifth in the Mid-Season Draft, can play at either end of the ground, with his precision kicking and excellent marking a feature to his game.
He has had to wait for his opportunity having come through the Gold Coast Suns' Academy program.
Speaking to reporters, Longmire believes their experience will help when counted upon.
"We picked up a couple of mid-season boys - Jack and Harry - and we had our first VFL win last week," the premiership coach told reporters.
"It was a really good game of footy and went right down to the last two minutes. They were great.
"Just to get two mature age, bigger bodies in our VFL team made a big difference and they did a great job.