Darron Gibson was the first United player to take aim at goal, but his curling shot deflected out for a corner. There were then shouts for a penalty on 12 minutes when Obertan's shot nicked off an arm on the way through to Hennessey but referee Lee Mason's refusal was immediate and adamant.
Summer signing Bebe started brightly and helped carve out a chance for Macheda on 19 minutes. The Portuguese bravely put his body on the line in a challenge with George Elokobi before reaching the loose ball first and crossing low into the penalty area. Macheda controlled the ball and shot through a crowd of players but his effort was straight at Wayne Hennessey.
Hennessey's opposing number, Ben Amos, endured a brief scare at the other end when a deep cross eluded the young goalkeeper. Wes Brown, captain for the night, was positioned well, though, and nodded the ball out for a corner.
Wolves' best chance in the first period came after Jonny Evans got himself into trouble and, in an effort to recover, tangled with Steven Fletcher 25 yards from goal. Former Red David Jones lined up the resulting free-kick but only succeeded in blasting the ball into the wall.
Evans' error arrived amid a sloppy 15 minutes from United's point of view. After a positive start, it was as if a switch had been flicked: the simple act of passing to a team-mate turned into a chore and too often players dribbled into crowded spaces or down dead ends. Lee Mason's half-time whistle at least offered a chance for Sir Alex to issue fresh instructions, and the Reds duly emerged re-energised for the second period.