Benitez on the attack but United storm on

Rafael Benitez provided more evidence of the antipathy he feels for Sir Alex Ferguson last night, as his Liverpool side's defeat at Old Trafford left their hopes of Champions League football next season looking increasingly forlorn.

Benitez reiterated his belief that Ferguson attempts to exert influence over referees and accused United's Antonio Valencia of diving to secure a penalty, during his analysis of a game which leaves his side sixth – four points off Tottenham Hotspur with a game more played. A potentially defining day's Premier League football took United back to the top of the table, four points clear of Chelsea, following El Hadji Diouf's equaliser against Carlo Ancelotti's side at Ewood Park. Chelsea are two points behind Arsenal with a game in hand on them and United, while Manchester City's edgy 2-1 win at Fulham boosted their challenge for a top four place.

The penalty-taker Wayne Rooney was carrying a pronounced limp as he left Old Trafford last night, though United were unable to confirm whether he had incurred an injury or exacerbated the inflammation to kneecap tendons which led Ferguson to question the striker's full role in England's friendly against Egypt earlier this month.

One of the fieriest opening 10 minutes of any league game this season prefaced United's 2-1 win. Benitez and Ferguson clashed on the touchline after Ferguson had appeared to suggest to fourth official referee Andre Marriner – who dismissed Nemanja Vidic at Anfield last October – that Javier Mascherano should have been sent off for the foul on Valencia which resulted in United's equalising penalty. After much finger-pointing the two men returned to their seats, though Benitez occupied Ferguson's technical area at times during the game. Asked about comments Ferguson had made in his press briefing last Friday, Benitez said: "Just on Friday? Which Friday? This Friday or every Friday? We know about the influence of Sir Alex in everything but these referees are very professional."

The managers shook hands at the end and Benitez let the touchline clash rest. "When you have different opinions, you have to express different opinions. He has his own opinion about everything," he said. But having seen the penalty incident three times, which resulted in Wayne Rooney scoring his 33rd goal in 39 games, Benitez declared it to be "very suspicious".

Park Ji-sung needed a stitch to his face after receiving a kick from Glen Johnson and Benitez was also unhappy about Gary Neville's challenge on Maxi Rodriguez during a typically fiery clash. But Torres' frustrating afternoon owed more to his own lack of self-control. "We [Torres and I] were talking about this. It's not easy every game," Benitez admitted. "There are [decisions [he] doesn't understand ... out on the pitch."

Ferguson was unhappy with Torres' fifth-minute opening goal – "he was unmarked; we didn't defend it well" – and insisted Mascherano should have been dismissed for the penalty incident as Mascherano was the last "defender". "There was no way [Jamie] Carragher could have got across to stop Valencia from shooting, absolutely no way." Rooney told his manager that he had "changed his mind" when depositing the penalty which Pepe Reina saved – only to convert the rebound. "I said: 'Never change your mind'," Ferguson joked. A fine cross from Darren Fletcher set up Park's winner on the hour.

The United manager declared it would be a battle to the last for a fourth successive title, despite Chelsea falling away of late. "I don't think anyone's getting away. We are all opening the door," he said. City could go five points clear of Liverpool and into fourth spot, still with one game in hand, if they beat Everton at home on Wednesday, and Benitez accepted that his fate was now in others' hands.