Lee Hughes had seemingly put the home side in control with two first- half goals but Reid's man fought back with strikes from Andy Melville, Michael Bridges and Kevin Ball. "That was not one of our best performances but for character and endeavour it was second to none," said Reid.
"You are not going to play well for 46 games but, from the amount of energy teams are expending trying to break us down, I know that in the last 20 minutes we are going to get back."
Reid added: "My players showed real character - they never gave up and that is a tremendous quality. West Brom kept shutting us down but I knew they couldn't keep it up for 90 minutes. That is what I told my players at half-time."
The Albion manager, Denis Smith, disappointed to have thrown the chance of victory away against one of his old clubs, felt there was still enough in the performance to point to a successful future. "I can take heart from that but I will probably be criticised for saying that because we lost," said Smith.
"We had enough chances to have tied it up. By next May the Sunderland players and management will have been together for three years. I have only been here for one year but I can see things starting to come together."
Ball crowned Sunderland's fine comeback with the winner four minutes from time.
Hughes's brace took his tally for the campaign to an impressive 14. But Sunderland came back strongly after the break with three superbly taken goals in 19 minutes from Melville, substitute Bridges and the hard-working Ball.
Hughes first got his name on the scoresheet as Albion sliced open the Sunderland defence in the 26th minute. James Quinn beat Michael Gray on the right and crossed into the heart of the Sunderland defence. Kevin Kilbane headed the ball down for the dangerous Hughes to stab a right- footed shot home.
Hughes, the pounds 4 million-rated striker, was on the mark again a minute before the break when he latched onto a ball booted up field by Andy McDermott. The striker then held off Paul Butler before firing another shot passed the Sunderland keeper.
But that was the end of Albion's celebrations.
Goals: Hughes (26) 1-0; (34) 2-0; Melville (67) 2-1; Bridges (80) 2-3; Ball (86) 2-3.
West Bromwich Albion: Miller; McDermott, Van Blerk, Flynn, Murphy, Carbon, Quinn, Bortolazzi (Sneekes, 77), De Freitas (Mardon, 80), Hughes, Kilbane. Substitutes not used: Angel.
Sunderland: Sorensen; Makin, Gray (Craddock, 46), Ball, Melville, Butler, Summerbee, Rae, Quinn, Dichio (Bridges, 60), Johnston (Mullin, 73).
Referee: R Furnandiz (Doncaster).
Bookings: West Bromwich Albion: McDermott, Carbon. Sunderland: Rae.
Attendance: 14,746.Reuse content