Saracens, striving for a top four play-off spot, looked assured of victory when they led London Wasps by thirteen points with ten minutes remaining in front of a 9,000+ crowd at sun drenched Adams Park.
Reddan sold a 71st minute dummy to score a try that replacement Mark Van Gisbergen converted and then in the fourth minute of added time made a clean blindside break for his second try that Van Gisbergen also converted for a last gasp victory.
It leaves Gaffney's side now just two points clear of fourth placed Wasps with two games to play and what is galling from Gaffney's point of view is that the win that looked likely for so long wouldn't have sealed their place in the play-offs but would have pushed them eight points clear of Wasps, their only pursuers for the final play-off spot.
Next up for Sarries is a home tie with Harlequins (next Sunday) and they will know exactly what is required from that contest because earlier in the day London Wasps will have entertained a Northampton side desperate for points to avoid relegation.
Then the final round of matches, sees Gaffney's side travel to Sixways to play Worcester Warriors while Wasps travel to Welford Road.