Giant centre-back N'Gala scored two headers against Rochdale in Pompey's last home game and rose highest once more to guide a Ricky Holmes out-swinging corner past Brian Jensen after just four minutes.
The Shakers, currently in the hands of stand-in boss Ronnie Jepson, improved after the break and would have been level 10 minutes into the second half but for a Phil Smith wonder-save to deny a close-range Harrad header.
The struggling visitors dominated the second half but after Hylton and substitute Anton Forrester missed good chances, they almost conceded again when Jed Wallace hit the post late-on.
- Sports & Recreation
- Shaun Harrad
- Ricky Holmes
- Danny Hylton
- Kevin Blackwell