Gylfi Sigurdsson, 27, was set to join the Toffees from Swansea based upon a gentlemen's agreement within the region of around £45m. However, disagreements upon the valuation of the Icelandic midfielder may lead to this transfer falling through.
The Telegraph report that their was a verbal agreement between the two Premier League clubs of the figure mentioned previously. Despite this, it is believed that the Toffees attempted to renegotiate the deal, which coincidentally led to the Welsh side demanding £5m more for the Icelander's services.
It was believed that a deal seemed to be imminent for the midfielder as Everton manager, Ronald Koeman, revealed on Monday that a deal was close to being complete.
However, the re-negotiations have begun to frustrate managers of both clubs. It is understood that Koeman is frustrated at the club's consistent failure to sign the Iceland international, whilst Swansea manager, Paul Clement, has openly stated that he wants the issue resolved before the beginning of the season.
The Icelandic midfielder demonstrated his importance within a struggling Swans side last season, notching nine goals and providing 13 assists for the Welsh side.
Despite this, Sigurdsson has made it very clear that he doesn't intend on staying at the Liberty Stadium next season. This became evident as he made himself unavailable for Swansea's pre-season tour of America, possibly to force a move through to Everton.
The Welsh side appear to be adamant of selling the midfielder for no less than £50m, which has caused fear for many Everton fans as it appears the deal may fall through due to differences in the valuation of the player between the two clubs.