Diego Poyet is determined to establish himself in Slaven Bilic's West Ham side this season and avoid another loan spell.
Sunderland have completed the signing of defender Adam Matthews from Celtic for a fee of £2m.
The Manchester United midfielder has been absent since December after it was revealed he was suffering from a chronic bowel complaint that had been affecting him for months.
Sir Alex Ferguson's previous statement on the matter suggested Fletcher would attempt a comeback at some point during pre-season and was hopeful his fellow Scot would make a full recovery.
On Monday night rumours began circulating that Fletcher had accepted he would never overcome the problem and was set to quit.
However, it is understood that the rumours are wide of the mark and that the 28-year-old remains on course to begin his comeback this summer as planned.
The news will be greeted with relief by both United and Scotland fans.
Fletcher's combative midfield presence was missed by the Red Devils during their 1-0 defeat to Manchester City at the Etihad Stadium on Monday night.
And Scotland boss Craig Levein is hoping to have his captain available for the early stages of autumn's World Cup qualifying campaign.