John Cofie netted twice with Ravel Morrison adding a third in a 3-1 victory for Warren Joyce's team, who continue to look in good shape during the pre-season.
Cofie opened the scoring out of the blue with a sensational strike, picking his spot from around 30 yards out with the ball crashing back out off the stanchion. The former Burnley striker should have doubled the lead but wasted a glorious opportunity and was punished when Alan Bull levelled five minutes before the break. United's response was instant as Cofie turned a defender and fired a low shot past Paul Smith to regain the lead and claim his second. Davide Petrucci also came close on a couple of occasions, firing just over the top before working Smith.
The torrential rain was an issue but the pitch held up well and the Reds almost extended their lead when Cofie came close to sealing his hat-trick. However, Morrison latched onto a pass from Paul Pogba to rifle an angled finish past Smith to give United some breathing space with 19 minutes left.
It was another good work-out for the visitors, against determined opponents in the Welsh champions, with the league campaign kicking off on Monday away to Arsenal.
United: Johnstone; Lingard, Giverin (Vermijl 69), Fryers (Leao 80), Fornasier; Drinkwater, Petrucci, Pogba, Mamam (Cole 57), Morrison; Cofie.