Last week's first ever meeting between the clubs saw Stoycho Stoev's Bulgarians claim a famous 1-0 victory at the Stadio Olimpico, thanks to Roman Bezjak's goal on the stroke of half-time.
The team from Razgrad won all but one of their group-stage games, conceding only two goals in the process, and Lazio learned first hand that goalkeeper Vladislav Stoyanov can often be an immovable object.
Therefore Reja, who is all too aware that his side must score in Sofia, is plotting an early assault on the Bulgarian goal.
He told a press conference: "We know how good our opponents are and so we must play a careful game, but an aggressive game.
"We have to take the game to them, we can't sit back and wait for them.
"It would be good if we could score in the first half, so we hope that their goalkeeper does not perform like he did in the first leg!"
Reja expects Italy keeper Federico Marchetti to be fit following injury, meaning Etrit Berisha drops to the bench, but defenders Andre Dias and Abdoulay Konko are sidelined.
Lazio's star players - who include Miroslav Klose, Lucas Biglia and Antonio Candreva - are all expected to play some part in Thursday's game and Ludogorets boss Stoev is suitably wary of experiencing a backlash in Sofia.
"They are a rich club that can afford very classy players," he said.
"Progressing in the Europa League is important for them because they may fail to qualify for next season's tournament through the league.
"I expect some very serious revenge from them, because nothing is decided yet."