The Rams appeared to be heading for a 2-1 victory at Fratton as the relegation clash entered six minutes of time added-on.
However, Rob Atkinson, who had earlier scored his maiden Pompey goal before putting through into his own net, rode to the rescue by heading home Nicolas Schmid’s long goal kick.
Days earlier the Blues lost in agonising circumstances at Coventry, now they had earned a precious point – and here are Neil Allen’s player ratings...
1. Nicolas Schmid - 7
Had no chance with either goal, with others responsible for letting the crosses come in. Unlikely assist provider too for Atkinson's stoppage-time equaliser. Photo: Jason Brown
2. Zak Swanson - 6
(Replaced on 78 mins by Terry Devlin) - The fact he was straight back into the side after two matches out injured demonstrates Mousinho’s faith in the right-back. Solid enough and out of position for the cross for the second goal. Photo: Jason Brown
3. Regan Poole - 7
Another whole-hearted display against another central-defensive partner, this time Rob Atkinson. Battled away manfully. Photo: Jason Brown
4. Rob Atkinson - 8 - MOM
Absolute warrior. A welcome return to the side after nine games injured and having only come back into training this week. Instantly makes Blues a better side, but no-one could see three goals. Of which one was obviously an own goal. Photo: Jason Brown