The scoreline didn’t tell the whole story after two late goals from United winger Tahith Chong added to a first-half double from Arnau Puigmal. Boro first-teamers Hayden Coulson, Marc Bola and Marcus Browne all started for Graeme Lee’s side and our Boro writer Joe Nicholson has rated their performances - scroll down and flick through our gallery to see who shone and struggled:
9. Stephen Walker - 5
Produced some good link-up play when he dropped deep. Kept in check by United's strong centre-backs. 5 Photo: Frank Reid
10. Sam Foralin - 5
(for Browne, 7) Made a few powerful runs on the flank but they didn't come to much. 5 Photo: Jan Kruger
11. Rumarn Burrell - 6
(for Liddle, 65) Didn't have many touches after coming on in the latter stages but took his goal well when the opportunity arose. 6 Photo: Frank Reid
12. Djed Spence - N/A
(for Folarin, 75) Introduced with 15 minutes to go. N/A Photo: JPI Media