The 30-year-old seam bowler claimed a career-best five for 14 as the Old Trafford side were rushed out for just 132 in reply to Northants' 235 all out on day two at the County Ground.
The home side had moved on to 25 for one - with Ricardo Vascocnelos the man out - before bad light brought a premature end to the day, a lead of 128 going into Thursday's day three.
It was a first five-wicket haul in first-class cricket for Cumbrian White in only his 12th appearance, the player having not made his professional debut until 2020 after being picked up by Northants while playing Grade cricket in Australia.
“Jack was magnificent," said Sadler. "All the bowlers were.
"They’ve been relentless for a long period of time now and Jack has just got better and better and better.
"It was a well-deserved maiden five-for. He was superb. All the bowlers were great, but led by Jack."
Sadler admitted he had felt Northants' first innings effort of 235 was a little light, but branded his team's bowling attack being 'on another level' as they rattled through Lancashire's batting line-up to put the County in the box seat.
“We wanted to score 250-plus really," said the head coach.
"So we were a little bit disappointed we didn’t get there but these things happen.
"Rob Keogh and Lewis McManus were tremendous on Tuesday to get us somewhere near. That partnership really got us in the box seat.
"But the way we went out and bowled, we wrestled the initiative back, particularly after lunch.
"I thought we were on another level and that's where we really got control of this game.
"We’d have liked to get a few more but if you'd have offered us a 128-run lead for one wicket down at this point we’d have snapped your hand off.
“We were relentless, we gave them nothing, we made them work and we created chances and put them under pressure and just kept asking questions ball after ball after ball.
"We backed up well in the field.
"The team spirit and the focus we've got as a group right now is something that, if we could bottle it up and keep it, it would be priceless.”
Play is due to start at 11am on day three.