It was the visitors who had the majority of the ball in the opening exchanges, but they failed to create any clear-cut chances. And Ferguson's men were made to pay as Vadaine Oliver handed Crewe the lead after just 15 minutes.
Six minutes later the hosts doubled their advantage as they hit lacklustre Peterborough on the counter attack. Oliver was again involved as his tackle in the Alex half allowed Lee Molyneux to serge forward down the left. The former Everton man then fired forward a stunning long ball which landed perfectly for Ajay Leitch-Smith to slot home.
Peterborough were handed a lifeline on the stroke of half-time when Tyrone Barnett reduced the deficit. Alex goalkeeper Steve Phillips could only palm Mark Little's shot into the 27-year-old's path, and he made no mistake with the finish as he rifled home his fourth goal of the season.
In second-half injury time Phillips then pulled off another excellent save from Lee Tomlin's long-range effort but, from the resulting corner, Posh captain Michael Bostwick bundled the ball home to grab a last-gasp point for the visitors.
The result maintained the Alex's unbeaten home record this season, but Davis also admitted his frustration at seeing his side let a two-goal lead slip.
"Whenever you're 2-0 down in a game and you get something from it, you deserve credit," Ferguson said.
"We kept going and scored late on, so credit to my players for coming back and getting something out of it.
"It was a brilliant start from us, we were in complete control of the game.
"Of course, goals change games and after their first two shots on goal, we were 2-0 down. It left us with a problem.
"But the goals on half-time and at the end got us a point. It's important when you have a defeat that you don't lose the next game, especially when you're trying to achieve what we are this season. We couldn't afford to lose two games on the bounce."