Will Keane, with his fourth goal in three games since returning from injury, got the ball rolling early on and two goals inside a couple of second-half minutes by the lively Adnan Januzaj and Wilfried Zaha, plus a late fourth by Larnell Cole, were the least the holders deserved for a dominant display.
Only Jay Lynch prevented an avalanche of goals in the first half as the former Reds trainee made a string of saves to keep his side in the game. When Will Keane sharply controlled and finished a Guillermo Varela cross inside two minutes, the writing looked on the wall for Wanderers but a combination of poor crossing and inspired goalkeeping ensured the scoreline remained 1-0 until the break.
Januzaj had a couple of wayward attempts and forced Lynch into a save from a free-kick before Zaha enjoyed a real purple patch. The ex-Crystal Palace winger twisted and turned his way into the box only to scoop off target and then set up Cole for a deflected drive that flew inches wide.
The bar came to Bolton's rescue when Zaha embarked on a terrific solo run and blasted in a left-footed shot as the hosts were pinned back throughout. The pick of Lynch's first-half saves saw him dive to parry away a Cole effort and he made further stops from Januzaj (twice) and Will Keane to frustrate the Reds' tidal wave of attacks.
The second half saw more of the same, constant United pressure, and the woodwork was rattled again when Tom Thorpe dived to meet a Januzaj cross. The teenager, a substitute for the first team on Saturday, added a second with a splendid strike by collecting a Cole pass, cutting inside onto his left foot and rocketing a shot into the