However, the Reds boss did not think Sir Alex Ferguson's pre-match suggestion that Liverpool benefited from many decisions other sides did not had a bearing on referee Howard Webb's handling of the game.

Striker Fernando Torres gave the visitors the ideal start when he headed in Dirk Kuyt's cross six yards out in the fifth minute.

However, referee Webb's controversially awarded a penalty five minutes later when Valencia went down under Javier Mascherano's challenge despite initial contact being outside the area.

Wayne Rooney converted the rebound after Jose Reina had brilliantly saved his spot-kick but it was not until midway through the second half when Park Ji-sung scored the winner from a diving header.

In the last minute Torres had a chance to equalise from 10 yards but ballooned his strike into the air and Yossi Benayoun headed tamely into goalkeeper Edwin van der Sar's arms.

"We gave away the penalty too early - but there are doubts about the penalty," said Benitez.

"When you see the replay it is suspicious how he went to the ground."

Asked whether he thought Valencia had dived Benitez said: "From the replay I think so.

"It is not clear but the way he fell strange.

"It made a big difference. We were playing well and had confidence and then one situation changed everything."

Benitez was involved with a heated touchline exchange with Ferguson after Rooney's goal, with his United counterpart suggesting Mascherano should have been sent off.

However, the Spaniard did not believe Webb had been influenced by Ferguson's comments prior to the game.

"Some decisions in the past have not been the best for us but I consider Howard Webb a good referee," he added.

"The referees are professional. We know the influence of Sir Alex in everything but he is a good referee.

"Jamie Carragher was coming inside so he was in the middle of the action (and therefore Mascherano should not have been red-carded)."

Of their touchline exchange Benitez said: "When you have different opinions you have to express them. He has his own opinion about everything."

Ferguson's opinion differed from that of Benitez.

"I thought it was a red card," he said.

"There was no way Carragher could get across and stop Valencia from shooting - he is took quick for Carragher to get across.

"The law is if you stop someone from having a goalscoring opportunity it is a red card. Not today.

"The referee was right, he tugged him down. He didn't bring him down outside the box; he didn't go down until he was inside the box. The decision was correct."

It was another occasion when Liverpool captain Steven Gerrard failed to perform as, apart from laying on the pass for Kuyt's cross for the goal, he failed to have a significant influence on the game.

There have been a number of games this season when the England international has failed to step up when the side needed him.

The sight of him being shifted from his central attacking midfield role to the left and then the right as Ryan Babel and Benayoun came on did not improve his body language, which has been poor for some time.

Benitez, however, chose to focus on the positives.

"It was a tight game and we had a good chance with Fernando or Yossi late on," he added.

"They (United) didn't create too many chances but they were always dangerous. It was close but the little things make a difference."

Without being close to their best, United ensured they will remain top, at least until Wednesday night when Chelsea play Portsmouth in their match in hand.

And whilst Rooney is gaining most of the plaudits for his goalscoring feats - he now has 33 following his 12th-minute equaliser - and man of the match Darren Fletcher emerged quite some time ago as an influential figure in the midfield battle, Park is also emerging as an unlikely hero for United.

The South Korean is ideally suited to Ferguson's preferred formation, with Rooney as a lone front-man.

And his diving header to cement all three points was testament to his willingness to run.

"Park is one of those players we can give roles to," said Ferguson.

"He has such intelligence and discipline. Today we found another role for him that was slightly different but was really important for us.

"He is such a brave little lad that his courage got him the goal."

As Carlo Ancelotti's men still have to come to Old Trafford at the beginning of next month, Ferguson's side are in charge of their own destiny.

Now Rio Ferdinand has revealed the full extent of the back injury that kept him out for three months - and from which he has now fully recovered - and, for the first time in four meetings with Liverpool, Nemanja Vidic managed to avoid a red card, Ferguson can look forward with confidence.

"We have a very experienced back four, a very experienced goalkeeper and that gives us a real outstanding chance, albeit with seven difficult matches - but we have all got difficult matches, so what does it matter?

"No-one is going away. We are all knocking on doors.

"If you look at the run-ins for the teams, it could very well go to the wire."