Albion, relegated along with Newcastle last season, had looked set to launch their promotion bid with a win after Shelton Martis gave them a 39th minute lead with his first goal for the club.
But Newcastle, without a manager and still searching for a new owner, showed their battling qualities to grab an equaliser through Duff ten minutes into the second half.
While Duff's goal ensured Newcastle a draw, they were probably more indebted to 21-year-old Dutchman Krul for their point.
Krul replaced the concussed Steve Harper at half-time and pulled off vital saves to twice deny Robert Koren and then Luke Moore and Graham Dorrans
Albion's frustration was summed up in the final seconds when Jonas Olsson had a goal disallowed for pushing.
Albion had made the breakthrough when Martis reacted fastest in a frantic goalmouth scramble.
Martis struck after Duff had fouled Koren on the left wing. Jonathan Greening swept in a free-kick that Harper punched clear under pressure from Olsson.
But Harper's clearance flew straight to Moore who drove the ball back towards goal. A ricochet off Olsson found its way to Martis, who stabbed the ball home from inside the six-yard box, despite the best efforts of Harper.
The goal proved to be painful in more ways that one for Harper who was struck on the head by the leg of team-mate Shola Ameobi and he needed lengthy treatment before he was able to continue.
Unsurprisingly, Harper did not reappear for the second half and his replacement Krul made an instant impact as he kept Newcastle in contention by keeping out Koren's shot.
It proved to be a decisive moment as Newcastle were on level terms shortly after when Ameobi picked out Kevin Nolan.
Nolan rolled a pin-point pass into the path of Duff and he beat Marek Cech to the ball before beating Scott Carson with a low angled drive.
Newcastle would only have been on level terms for two minutes had it not been for Krul, who pulled off a one-handed save to keep out a drive from Koren, before blocking a goalbound drive from Moore.
Newcastle should have really cashed in on Krul's heroics but the unmarked Nolan headed wastefully over the bar 11 minutes from time.
That miss would have been costly, but again Newcastle were saved by Krul when he superbly tipped Dorrans' volley over the bar.