Manchester United manager Sir Alex Ferguson revealed that he has been working on a list of summer transfer targets for a number of months as he looks to add more quality to his title winning squad.

The Telegraph reports that Ferguson is keen to make some minor adjustments over the course of the summer, with suggestions that out-of-favour midfielders Anderson and Nani will both be allowed to leave the club.

Nani and Anderson
Could Nani and Anderson both be heading out of Old Trafford this summer? [Reuters]

Neither has managed to establish themselves as regulars in the first team this season, with Anderson particularly struggling as Phil Jones has often been preferred in a central midfield position, while Ferguson is also keen to hand more opportunities to youngsters Nick Powell and Adnan Januzaj.

Portuguese winger Nani has also fallen out of favour and found his playing time restricted this season as he has made just 10 Premier League appearances, compared with 29 in the previous campaign.

Should Ferguson be prepared to let the duo leave then it seems he may already have replacements in mind as he admitted that his staff have been working on identifying talent for some time.

"Hopefully, the players we bring into the club in the next year or so will be of the quality we need," said Ferguson, as quoted in the Telegraph. "We're competitive in the market - we're not Chelsea or Manchester City in terms of money but we're competitive.

"We've been doing a bit of work on recruitment over the last three or four months, targeting who the players are that we feel could enhance us, make us better or help us maintain the level we're at."

United have been strongly linked with Porto winger James Rodriguez in recent months but Ferguson has always maintained that the Colombian's transfer fee would simply be too high.

However, should United cash in on Nani and Anderson then he may well be prepared to meet Porto's asking price, which is believed to be around £36million.

Another player that has been linked with Manchester United for over a year is Borussia Dortmund striker Robert Lewandowski who has just over 12 months remaining on his current contract.

The Poland international appears unlikely to remain at Dortmund beyond his current deal and there has been plenty of speculation suggesting that he will either join United or Bundesliga champions Bayern Munich.

A move to Old Trafford may well be appealing to Lewandowski who would be able to join up with former teammate Shinji Kagawa.