Macheda's 'little boost' for big trip to Porto

It has come to something when what we do know is outstripped by what we don't. But this is the case with Manchester United.

What we know is that goals from Paul Scholes and Federico Macheda gave United victory at Sunderland on Saturday to restore their single-point advantage over Liverpool at the top of the Premier League (and United have that game in hand), which means a third consecutive title looks bound for Old Trafford. What we also know is that, on Sunday, United have an FA Cup semi-final against Everton, having already won the League Cup. Another thing we know is that United are the European champions.

And yet what we don't know is how United are going to play at Porto on Wednesday night. Overriding our knowledge of United's formidable and successful experience is a sense, a suspicion, that they are not the team they were as recently as 32 days ago when they were eliminating Internazionale from Europe with a show of strength.

Since then United have lost to Liverpool and Fulham, relied on a 17-year-old Italian for late winners against Aston Villa and Sunderland and drawn 2-2 at home to Porto in the first leg of the Champions League quarter-final. This is why Ferguson referred on Friday to United's situation as "strange".

Saturday did not clarify matters. United won and in Wayne Rooney had a player on top of his game; Macheda came off the bench for the second time in six days to score a winning goal ("you'll win nothing with kids") and Scholes scored a vintage opener.

Yet Porto's scout will have departed Wearside comforted by the sight of United defenders – players of the calibre of Nemanja Vidic and Gary Neville – providing the odd shank and being troubled by a Sunderland team that had scored twice in six matches.

Five minutes before half-time here, with United one up through Scholes' exquisite header, Vidic diverted a Carlos Edwards cross on to Ben Foster's post. An inch to the right and the ball might have gone in. Vidic, so imposing a month ago, appeared startled. We do not know how he will perform on Wednesday.

Sunderland had identified John O'Shea as vulnerable at left-back, to judge by the times Edwards and Phil Bardsley attacked down that flank. It worked.

Late in the game, after Macheda had diverted Michael Carrick's shot beyond Craig Gordon 46 seconds after replacing Dimitar Berbatov, Neville and Jonny Evans gave the ball away on the edge of their own area. Sunderland could not profit, but could Porto?

It would be an exaggeration to say United were seriously wobbling but the odd tremor was why Ferguson used the word "sloppy".

There was a short shift from Cristiano Ronaldo after he came on for Park Ji-Sung on 67 minutes, for a spell that included some tackling back. Given that Ferguson has admonished Ronaldo for waywardness seen against Porto – "In European football, if you give the ball away it takes a long time to get it back," he said when referring to Ronaldo – this was the dedication he wanted.

So Ronaldo is fit. Ferguson will have Rio Ferdinand back to partner Vidic in Oporto. Patrice Evra will return on the left and Edwin van der Sar in goal. That should stabilise defence.

But while Kenwyne Jones and Djibril Cissé played better than of late, and Jones poked in a 55th-minute equaliser after a self-confessed "fumble" by Foster, Porto will offer more than a team which has lost four in a row.

There was a minor admission from Scholes: "It's always nice to get a win. It always boosts your confidence. I think we needed a little boost today."

Sunderland have also been boosted, if not by the result, then by a good performance. Manager Ricky Sbragia needed that. Sunderland now face Hull at home on Saturday before travelling to West Bromwich, two fixtures that could decide what happens next on Wearside, and not just this season, but for some time to come. Old Trafford has no monopoly on uncertainty.

Goals: Scholes (19) 0-1; Jones (55) 1-1; Macheda (76) 1-2.

Sunderland (4-4-2) Gordon; Bardsley, Davenport (McShane, 73) Ferdinand, Collins; Edwards, Leadbitter, Tainio (Yorke, 85) Reid (Murphy, 80); Cissé, Jones. Substitutes not used: Fulop, Ben-Haim, Malbranque, Colback.

Manchester United (4-3-3): Foster; Neville, Vidic, Evans, O'Shea; Park (Ronaldo, 67) Carrick, Scholes; Tevez (Anderson, 82) Berbatov (Macheda, 75) Rooney. Substitutes not used: Kuszczak, Evra, Giggs, Nani.

Booked: Sunderland Ferdinand; Manchester United Neville, Rooney.

Referee: R Styles (Hampshire).

Man of the match: Rooney.

Attendance: 45,408.