The Auckland fast bowler picked up two wickets in two balls and finished with a career-best haul of seven for 34 to put the Aces in a strong position in their Plunket Shield clash at Eden Park Outer Oval.
Ferguson ripped through Otago's top order on the opening day and returned yesterday to snaffle another three wickets to help wrap up another disappointing Otago batting effort.
The Volts reached a modest 170 in reply to Auckland's first-innings total of 213.
That small deficit has grown steadily with Auckland reaching 162 for two at stumps on day two.
Otago trails by 205 runs and needs quick wickets to get back in the match.
''Ideally, we would get one or two wickets before the new ball arrives in nine overs' time and try to get through the rest of the order before they do too much damage,'' Volts coach Rob Walter said.
''The pitch is definitely getting better and better. We are certainly up against it ... but I don't think a chase of 350 would be out of reach.
''We still have to believe that we have a chance; we just have to nail down the first session [this] morning.''
The Volts resumed on 83 for five with a salvage job ahead.
Ferguson was quick to pick up where he left off. He nabbed four wickets in eight overs on Tuesday and struck again almost immediately.
He bowled Derek de Boorder before he was able to add to his overnight score of 14. It was Ferguson's eighth five-wicket bag and he celebrated with a bouncer to Mark Craig, who was powerless to do anything other than steer the ball to first slip.
Ferguson had taken two wickets in two balls and the visiting side had slumped further to 84 for seven
Anaru Kitchen added a much-needed 44 and Neil Wagner counterattacked with an undefeated 39.
But the Volts conceded a first-innings deficit of 43 runs which, in the context of the game, was more significant than it sounds.
''The reality is he [Ferguson] bowled particularly well. The dismissals are there for everyone to see ... and there were some pretty serious deliveries.
''In one respect we are disappointed with portions of our batting but you also have to give credit when it is due. He bowled exceptionally well.''
Competition leader Wellington appear poised to secure a useful first-innings lead in Hamilton.
The visiting team posted 380 and, in reply, Northern Districts is 237 for seven.
In Christchurch, Central Districts is in a commanding position.
The Stags declared at 498 for seven. Former Black Cap Jesse Ryder added 88 to go with the centuries Greg Hay and George Worker made on the opening day.
Canterbury is in trouble at 98 for four in reply.
