Larnell Cole's early strike proved decisive and first-teamer Tom Cleverley got 90 minutes of action under his belt as United ensured a top-three finish in the table ahead of the final group fixture with Liverpool, which is also being played at the Theatre of Dreams.
The Reds were quickly into top gear and a delightful move exploited space down the Baggies' right flank. Alex Büttner broke forward to collect a Cleverley pass before feeding Jesse Lingard and an inviting centre was slid into the net from close range by Cole.
Only Luke Daniels prevented the hosts from falling further behind as he made smart stops to frustrate Lingard and Cole but West Brom battled their way back into the game. A brave save by Ben Amos kept out Adil Nabi before the keeper was worked again by Romain Sawyers' header.
When Amos was beaten all ends up by a Scott Allan drive, fortunately for Warren Joyce's side, the ball cannoned back off the left-hand post. After the break, Lingard continued to look the liveliest forward on show as he saw a shot scrambled away by Daniels before coaxing a delicate curler off target.
Büttner joined the attack to good effect again but hammered his centre across the face of goal and the Dutchman later made way for Reece James. With the Reds coping comfortably with the threat posed by former Manchester City man David Oldfield's team, an intricate move led to another attempt by Lingard that drew a save out of Daniels.
After the visiting keeper dived to beat out a Ryan Tunnicliffe effort, his side mustered a chance at the other end but Aaron Birch drilled over the top from outside the box. However, it proved to be a largely isolated attack as United kept