Leicester City have been dealt a significant setback in their quest to replace new Chelsea midfielder Danny Drinkwater amid fears that they will now have to wait until 2018 to see final summer signing Adrien Silva in action.

The Foxes eventually sold Drinkwater for £35m ($45.6m) at the 11th hour of a hectic deadline day after weeks of negotiations and quickly turned their attentions to Silva, eventually announcing some 20 hours after the summer window closed that they had agreed terms with Sporting Lisbon over a deal said to be worth £22m. They were initially granted a two-hour extension in order to complete all the necessary paperwork.

However, it was reported on Tuesday (5 September) that the transfer remained in the balance due to Fifa having yet to approve his registration.

The BBC now claim that Fifa have indeed rejected Leicester's attempt to register Silva after they missed the deadline by just 14 seconds.

With Sporting president Bruno de Carvalho eager to stress that the transfer itself was finished in time, it appears that the 28-year-old could remain in limbo until January if no amicable solution can be found.

"We are working with Adrien and Sporting Clube de Portugal to overcome some issues relating to the player's registration and exploring all options to find a resolution," a Leicester spokesman told the BBC.

It had originally been hoped that Leicester would complete all the formalities of the Silva deal before the weekend, when the French-born Portuguese international would probably have been in contention for Saturday's Premier League visit of Chelsea to the King Power Stadium.

In his absence, manager Craig Shakespeare seems likely to continue with a central midfield partnership of Matty James and Wilfred Ndidi unless £10.5m July arrival Vicente Iborra is fit to play for the first time this season following a groin injury. Andy King and Daniel Amartey are Leicester's other options in that area.

Drinkwater had yet to feature for Leicester in 2017-18 due to his own groin issue, yet should be available to make an immediate return to the East Midlands after being pictured training alongside the likes of David Luiz, Tiemoue Bakayoko, Cesc Fabregas and Marcos Alonso at Chelsea's Cobham training base on Monday.

Fellow deadline day signing Davide Zappacosta may also be included in Antonio Conte's squad to face Leicester following his surprise £23m switch from Torino, although it could be more likely that the duo make their debuts on Tuesday night when Chelsea mark their Champions League return with a home clash against Azerbaijani debutants FK Qarabag at Stamford Bridge.

Adrien Silva
Adrien Silva could be ineligible to play for Leicester until January 2018 Carlos Rodrigues/Getty Images