9? nah mate, it's theoretically possible to have 12+ (not all in one round though without opponent 'help')... Operator, Summoning Circle, Eredin, Muzzle... but they'd be hell to get out... need decoy for the navigator, Recons, Alzhur's DC, and Avalach.
I regularly put out 5-6 with a Nova version of that deck...
and if you think that's sick, it's theoretically possible to hit 14 Queensguard's with a NG Slave Robber deck
it's also still possible to hit 18+ Slave Infantry in a single round
Kaeweni Knights can pretty much fill a board
... and then there's bonuses from Create RNG
PSA: is somone Operator's you a copy of a unit, especially that has an ability that can be triggered AFTER it's played.... don't play it while they still have cards in hand or haven't passed... odds are they'll copy it then steal yours