One man’s pain is often another man’s gain. While Rafael Benítez, the Liverpool manager, will doubtless have again seen a conspiracy after watching Manchester United benefit from some questionable refereeing decisions against Blackburn Rovers to keep up the pace at the top of the Barclays Premier League, José Mourinho, the Inter Milan coach, must have been secretly rubbing his hands with glee at what unfolded at Old Trafford on Saturday.

Benítez’s infamous rant at Sir Alex Ferguson last month may have been ill advised, but his belief that the United manager wields an unfair influence over match officials will only have been strengthened by the performance of Howard Webb, the referee, who seemed as intimidated by the Old Trafford surroundings as so many opposing teams have been this season.

Morten Gamst Pedersen, the Blackburn winger, claimed that too many sides were “scared” of United, but just about stopped himself from saying that referees are, too. There could be few other reasons, however, to explain why Webb failed to send off Cristiano Ronaldo before the Portugal forward had the chance to blast a winning free kick past Paul Robinson or award Blackburn a penalty and dismiss Rafael Da Silva after Pedersen was given just enough of a helping hand by the United right back to go to ground with the visiting team trailing 2-1.

Ferguson, naturally, attempted to dismiss both incidents, although perhaps the main talking point was the transformation of United’s defence from the meanest rearguard around to a jittery wreck that a Blackburn team in the midst of a relegation battle succeeded in picking off without getting the reward their efforts probably deserved.

United had not conceded a goal in their 14 previous league matches, but their defensive disarray was such that Mourinho is likely to take great encouragement ahead of the first leg of Inter’s Champions League first knockout round tie against United at the San Siro tomorrow. The former Chelsea manager’s mood will have improved further with the news that the European champions could have only one recognised central defender — Rio Ferdinand — available as Ferguson wrestles with injuries to Wes Brown, Gary Neville, John O’Shea and Jonny Evans, and the suspension of Nemanja Vidic. It was always going to be interesting to see how United reacted once their defence was finally breached, but Roque Santa Cruz’s goal — the first conceded by Ferguson’s team in the league for a British-record 1,334 minutes — seemed to send them into a tailspin.

Ferguson has rarely strayed from his seat in the stands in recent months, such has been the ease with which United have brushed aside the opposition. It said everything about the threat Blackburn posed that the United manager was glued to the touchline in the second half, barking orders at Ferdinand for not communicating with Rafael, before throwing on Vidic in the hope of shoring up his defence after Evans limped out.

After Santa Cruz had equalised in the wake of Wayne Rooney’s opening goal, Blackburn should have taken the lead in the 58th minute when Ryan Nelsen hit a post and then El-Hadji Diouf’s shot on the rebound was smothered by Tomasz Kuszczak, deputising none-too-convincingly in goal for Edwin van der Sar.

Ronaldo has had a habit of petulantly kicking out at opponents this season. He has done it to Scott Brown, of Celtic, Andy Wilkinson, the Stoke City defender, and Michael Dawson, of Tottenham Hotspur, and now add David Dunn to that list. The Blackburn midfield player was deliberately clipped around the shins by Ronaldo in the 56th minute — in clear view of Webb — but the referee did nothing when at least a yellow card was warranted. Seconds later, Ronaldo was booked for a dive and a few minutes later he thumped in a free kick that Pedersen, for one, wondered if he should still have been around to take.

So United press on, defeated only once since November 8, but Mourinho may have spotted a chink in the armour.

Manchester United (4-2-4): T Kuszczak 6, Rafael Da Silva 4, R Ferdinand 5, J Evans 6, P Evra 6 - M Carrick 6, P Scholes 5 - C Ronaldo 6, D Berbatov 6, W Rooney 8, Nani 6. Substitutes: C Tévez 5 (for Nani, 64min), N Vidic 6 (for Evans, 64), R Giggs (for Scholes, 82). Not used: B Foster, D Welbeck, Fábio Da Silva, D Fletcher. Next: Newcastle Utd (a)

Blackburn (4-5-1): P Robinson 5 - A Ooijer 7, R Nelsen 6, G Givet 7, S Warnock 6 - E-H Diouf 6, K Andrews 5, V Grella 6, D Dunn 5, M G Pedersen 6 - R Santa Cruz 7. Substitutes: Tugay Kerimoglu (for Dunn, 73min), B McCarthy (for Grella, 79), K Treacy (for Diouf, 83). Not used: J Brown, Z Khizanishvili, A Mokoena, J Roberts. Next: Hull City (a)

Referee: H Webb Attendance: 75,000