Manchester United manager Sir Alex Ferguson has warned his players they cannot afford to be so careless in front of goal.The Red Devils have found the target just twice in their last three games in all competitions, with both goals coming from Portuguese ace Cristiano Ronaldo.

It was the winger who came to the rescue at the weekend, as United made hard work of scraping past rock-bottom Derby.

The league leaders spurned a whole host of chances at Pride Park, a week after seeing countless opportunities go begging in their FA Cup quarter-final defeat to Portsmouth, and Ferguson has now admitted that the inept finishing is beginning to worry him.

"The missed chances are becoming a concern," the United boss said in the Daily Star.

"We were really charitable against Portsmouth and against Derby. It's a sticky spell in front of goal that we must get over.

"Against Derby, we made it hard for ourselves because we missed so many chances. It turned into a real battle and it shouldn't have been."

United will have the opportunity to stretch their lead at the top of the Premier League to three points on Wednesday when they welcome Bolton to Old Trafford.

With the Trotters currently struggling towards the foot of the table, Ferguson hopes that his side will be able to rediscover their goal scoring touch in time for their date with Liverpool this weekend.

"There are important games coming up. We want to start taking our chances," he said.

"We want to drive home our advantage at the top of the league by winning our game in hand."

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