An inspired substitution from the Posh boss paved the way to victory at London Road - a result which came complete with a fourth league clean sheet in a row.
Ferguson's decision to unleash Nathaniel Mendez-Laing from the substitutes' bench reaped spectacular rewards as the winger fired the only goal of the game in the 64th minute, barely two minutes after his introduction.
Mendez-Laing collected a pass from skipper Tommy Rowe, cut inside from the left flank and steered a 20-yard shot past Shrews goalkeeper Chris Weale.
Posh were not at their best after on-loan striker Paul Taylor curled a second-minute shot against the post. Tyrone Barnett and Michael Bostwick both wasted golden opportunities with headers from Danny Swanson corners before Mendez-Laing made the breakthrough.
Peterborough were reliant on a superb late save from Bobby Olejnik to keep out a stinging Jon Taylor shot and preserve their slender advantage
Ferguson said: "I told the players that someone needed to step up to win the game and Nat did that after coming on.
"But I must admit I didn't really like the atmosphere in the ground at times. I feel our fans are quite disrespectful to the league. They can't think we're going to win 6-0 every game because that just doesn't happen.
"My players get nowhere near enough credit from the media either. We've won 10 games out of 12 after going to the wire in the Championship last season.
"Everyone is talking about Leyton Orient, but not us even though we are only one point behind them.
"This is a really tough league and our start is some achievement. People should maybe start realising that."