Manchester United face a tough challenge against Arsenal in their first-leg Champions League semi-final.
|Vidic is aware of the recent lack of consistency of the United defence [GALLO/GETTY]
United centre back Nemanja Vidic has fears the club may be denied a second successive Champions League final if they fail to sure up their leaky defence.
The three-time European champions host their English rivals in the first leg, four days after a dramatic 5-2 victory over Tottenham when they overturned a 2-0 deficit in the second half.
Before that match, United's back four had looked to have regained their durability by keeping three straight clean sheets after leaking 12 goals in five matches.
Vidic said that slump came as a result of Alex Ferguson's need to rotate the squad amid a tough match schedule.
"In the first half (against Tottenham) we didn't defend very well," Vidic said.
"In the second half we came back much stronger, and that is how we need to play against Arsenal and any team we play against.
"It just happens - sometimes things go wrong.
"We will try to fix the problems we have had in the last games, but we need to remember as well that we have changed many players.
"We have not played with a consistent team at the back, even in the middle or up front.
"We have so many games that sometimes you have to change the team and sometimes you need time to adapt."
What encourages Vidic, though, is the five-goal surge that kept United top of the English Premier League and boosted the strikers' confidence ahead of their first European encounter with Arsenal.
Ferguson has a tough decision about which strikers will start at Old Trafford.
Wayne Rooney, Cristiano Ronaldo and Dimitar Berbatov all scored in the 5-2 win, but second-half substitute Carlos Tevez was the architect of the comeback.
"We have the first game at home so we need to do well, we need to score goals, we especially have to improve on what has not been good in the last few games," Vidic said.
"To not concede a goal is very important, but we have players who can score, players who believe in themselves.''
The Serbia centre back said his main challenge on Wednesday will be to contain striker Emmanuel Adebayor.
"He's a great player and has the ability to score," Vidic said.
"He is big and strong and in that respect you have to expect a hard game against such an opponent."
Arsenal head north to Old Trafford in bullish mood after extending an unbeaten Premier League run to 20 matches by beating Middlesbrough 2-0 on Sunday, which all but secures another top-four finish and Champions League qualification.
|Adebayor will be a big target for the United defence [GALLO/GETTY]
"For me I am not scared of any team. I know what I have to do when I play," Arsenal defender Kolo Toure said.
"There is more pressure on United because they are the team to beat.
"United are the ones who won it last season, but for us we are going there to do the best we can playing free and passing the ball.
"We know when we play football against Manchester United, they struggle a lot."
The Gunners have already beaten United this season, recording a 2-1 win at
Emirates Stadium in November.
"United are a really good team going forward, but, like us, at the back they have conceded a few goals," Toure said.
"We have the same type of team - we both like to play, but sometimes you can be caught out at the back.
"The team that will win will be the one which defends the best. It is going to be a really big fight."
The 28-year-old Ivory Coast centre back is the last remaining regular from Wenger's "Invincibles" side which went undefeated for the entire 2003-04 season and one of only four players in the current squad who appeared in the 2006 Champions League final loss to Barcelona.