Manchester United recovered from going two goals behind to eventually see off a spirited Sporting Braga side 3-2 even if their defensive performance was again suspect in the first half.
A change of formation and an increased tempo in the second half enabled Manchester United to go clear at top of Group H with three wins on the bounce but still their defensive frailties are a concern.
Braga easily coasted into a two goal lead as United struggled at the back and failed to trouble their opponents in attack.
Sir Alex Ferguson played his much vaunted diamond system but United initially failed to cope with their new formation and the speed of their Portuguese opponents Sporting Braga.
Michael Carrick played at centre back and immediately failed to deal with a through ball which led to a corner, and whilst a goal did not result from the set piece the ball broke to former Newcastle player Hugo Viana who whipped over a cross from which Alan easily out jumped Alexander Buttner to head firmly home with just 85 seconds gone.
United looked unsure at the back and were punished 20 minutes later as Carrick was easily beaten to the dead ball line and the resulting cross was slotted home by the Brazilian for his second strike.
Both Robin van Persie and Hernandez then had opportunities to level as the home team began to assert their authority whilst still looking uneasy when the visitor's broke.
The host's continued to press after the break and were rewarded just after the hour mark as Van Persies corner was scruffily turned over the line by Jonny Evans.
At this stage Braga were defending in depth and keeper Beto made a fine save from substitute Nani to prevent United taking the lead. But the Red Devils were not to be denied as Tom Cleverley,s deep cross was finished by Hernandez to complete the comeback.
Referee: Milorad Mazic (Serbia)
Venue: Old Trafford
Man Utd scorers: Hernandez 25, 75, Evans 62
Braga scorers: Alan 2, 20
Yellow cards: Vinicius (BRA), Elderson (BRA)