With Joe Rodon ineligible and Mourinho regarding Japhet Tanganga as a full-back, Eric Dier may have to continue in the heart of defence – even if it would be preferable to rest him for Chelsea on Sunday.
Tanganga could make his second appearance of the season at right-back, with Matt Doherty not ready to start after contracting coronavirus on international duty.
In midfield, Mourinho will be hoping Harry Winks has recovered from a knock, while Pierre-Emile Hojbjerg could continue after a quiet international break.
Giovani Lo Celso will likely be given the chance to build on his goal-scoring display against City.
Mourinho will surely ring the changes up front, where Carlos Vinicius, Gareth Bale and Lucas Moura all need minutes, although he will not be shy about introducing Harry Kane and Heung-min Son from a 12-man bench if the deputies fail to dazzle.
Joe Hart and Hugo Lloris have tended to rotate in goal for the Europa League, but the former England No.1 will be hoping for a rare opportunity against the Bulgarians.
Tottenham predicted lineup (4-2-3-1): Hart; Tanganga, Sanchez, Dier, Davies; Hojbjerg, Winks; Lucas, Lo Celso, Bale; Vinicius.
Venue: Tottenham Hotspur Stadium
Referee: Giorgi Kruashvili (GEO)
Tottenham squad from: Lloris, Hart, Austin, Whiteman, Doherty, Aurier, Tanganga, Reguilon, Davies, Dier, Sanchez, Cirkin, Hojbjerg, Winks, Sissoko, Dele, White, Clarke, Lo Celso, Ndombele, Lucas, Bergwijn, Bale, Son, Kane, Vinicius.
Doubts: Doherty (fitness)
Injured: Lamela (achilles), Alderweireld (groin)
Ineligible: Gazzaniga, Rose, Rodon, Gedson