Aided by the conditions after the teams changed ends, Sunderland started the second half in the ascendancy. However, Jacob was equal to their best efforts, including one vital intervention to thwart James Brace, and Thomas hit the woodwork.
But the Wearsiders stunned the hosts with a quickfire double in a matter of seconds as Ross Holland blasted in a speculative long-range drive and then Thomas was left in the clear to curl past Jacob with his left foot for 3-3. Luke Hendrie had one shot saved by Dixon, van Velzen slipped with the goal at his mercy in the closing stages and Kenji Gorre also worked the Black Cats' keeper as United were unable to regain the lead.
With Barmby receiving treatment after being replaced, there could be a doubt over the top scorer's involvement in Friday's game at Old Trafford and captain Luke McCullough was also substituted towards the end.
United: Jacob; Grimshaw, Dalley, McCullough (Rowley 88), Blackett; Barmby (Gorre 65), Rudge, Pearson, Daehli (Hendrie 65), van Velzen; Wilson. Subs not used: Coll, Wilkinson.