Parnell led the way as Yorkshire were rushed out on the opening day of the LV= Insurance County Championship clast at Headingley, with Northants then closing on 36 without loss in reply, a deficit of 170.
The South African left-armer ended with five for 64, but there were also three wickets for Gareth Berg and two for Ben Sanderson, with Tom Taylor sending down 14 tight overs for just 34 runs.
And Liddle says it was the way the attack bowled in partnerships that put the pressure on Yorkshire, who were on the back foot from the first ball of the match when Sanderson bowled the in-form Adam Lyth for a duck.
And he also admitted the fact skipper Ricardo Vasconcelos won the toss and chose to bowl was a pretty crucial.
“It was definitely a positive move for us to bowl first.," said Liddle.
“We looked at the wicket and felt there was a bit in there for us, and we know that when our bowling attack clicks it will be tough for any team we play against.
“We’re happy with the score at the end of the day.
“One of the things we speak about is starting overs and starting spells well, and Ben Sanderson bowled beautifully and could have easily had a five-for himself.
“Wayne deserved his five wickets, but we bowled very well in partnerships.”
Yorkshire did initially recover from losing Lyth early on, with Tom Kohler-Cadmore, who hit 42, and Will Fraine - who replaced the rested England captain Joe Root in the team - taking them to 66 for one.
But they then slumped to 80 for five, before Dom Bess with 56 guided his team to 160 for six, but the late an lower order then fell away.
Kohler-Cadmore was impressed by the Northants bowlers, but he also insisted that Yorkshire's 206 could yet prove to be a par score.
“The ball’s moved around all day," he said.
"Credit to their bowlers that they kept testing our forward defences and hammering away. They bowled nicely and put us under a lot of pressure.
“You’d always want more on the board, but I reckon we’d be about par with 200. I feel that’s competitive if we can get it right with the ball.
“Hopefully we can have a good day tomorrow and turn it into a one-innings game.
“It was the last thing everyone was expecting the way Lythy’s seeing the ball (out first ball of the match). But it shows how much of a leveller cricket is.”