Boro boss Gareth Southgate is expected to strengthen his squad in January as his Riverside club face a battle against relegation and play to use Hulse to rescue them from the drop.
The striker joined the Blades 18 months ago - netting eight goals in top flight until he broke his leg at Chelsea in a 3-0 defeat in March and has only since recovered. He is expected to complete a £2,200,000 move to Tee-Side.