Sunderland's deal for Diafra Sakho on if West Ham can conclude capture of striker Carlos Bacca

Sam Allardyce’s patience has been tested during a chase for Sakho that has stretched on for more two months after Sunderland saw a formal bid rejected by the Hammers at the start of June.

West Ham have been unprepared to let Sakho go until they have landed a replacement frontman, with the Senegal international becoming so frustrated by the situation that he submitted a transfer request last week.

However, West Ham have been in talks Milan over a £26million deal for Colombian international Bacca.

Bacca’s agent, Sergio Barila, met with West Ham in London last night to discuss personal terms, although they are not thought to have reached an agreement yet.

But if the Hammers can seal the move for Bacca, it would pave the way for Sakho to depart, with the 26-year-old thought to favour a reunion with his former boss Allardyce, despite interest from West Brom, Watford and Crystal Palace.

An increasingly impatient Allardyce – again the subject of intense speculation over the England vacancy yesterday – left Sunderland’s pre-season training camp on Monday morning to return to the UK and help the Black Cats finally make their first signing of the summer.

But if Sunderland can ultimately seal a deal for Sakho, it would represent a major boost after a big chunk of the summer budget has been set aside for the frontman.

Allardyce is equally keen to land a new right-back after Sunderland’s proposed move for Inter Milan’s Davide Santon fell through last week.

Sunderland were yesterday linked with a surprise £4million move for former loanee Danny Simpson, just two months after he lifted the Premier League title with Leicester.

Simpson - unbeaten in his 14 appearances for Sunderland in the 2006-07 promotion-winning campaign - only has 12 months remaining on his contract with the Foxes, despite talks over a new deal beginning last month.

But there are major doubts over whether Leicester would sanction Simpson’s departure, or if he would be willing to leave the reigning champions.

The 29-year-old only made one Premier League start under Allardyce when he took charge at Blackburn midway through the 2008-09 campaign.