Soyuncu, 24, could miss three months with an abductor injury he picked up on international duty with Turkey.
Top scorer Vardy, 33, has a calf issue and missed Sunday’s loss to Villa.
Forward Islam Slimani, 32, was left out of the European squad despite featuring for the first time since January 2018 on Sunday.
“There’s no doubt that with all the games that we’ll have to make changes. But our squad isn’t deep enough to make wholesale changes because of the number of injuries that we have,” said manager Brendan Rodgers.
On Slimani’s absence in the squad, he added: “The squad had to be handed in much earlier than the Premier League squad and unfortunately, thinking maybe he [Slimani] wasn’t going to be here, that’s the reason why.”
Leicester will also be without midfielder Wilfred Ndidi, 23, who has a hip injury and Ricardo Pereira, 27, is a long-term absentee with an Achilles injury.
Leicester, who finished fifth in the Premier League last season, also face Braga and AEK Athens in Group G.
“The first job is to get out of the group stage,” said Rodgers. “We worked so hard last season to be in this competition, and it’s been brilliant that we got the qualification. Now we want to embrace it and enjoy it.
“We anticipate a really tough game. Watching their games against [Dynamo] Kiev and Shakhtar – they play a diamond which is difficult to play against.
“They play it out well, and the front two are clinical. But it’s what you expect, when you play in Europe you’re playing against the top clubs from their countries.”
‘A target to get into Europe’
Leicester City defender Jonny Evans: “It’s been a target at the club to get into Europe and we managed to achieve it. It’s a pity the fans can’t be there to share the experience with us. We know it will be a tough group to get out of but we’re confident, especially if we get off to a good start.
“Travelling around Europe with your team-mates and going to the different stadiums, you never get that back. They are great occasions, we have been looking forward to it and I’m sure we’ll relish it.
“They’ve been in the Europa League before so they’ll be more experienced in that respect. But it’s a home game, we want to get off to a good start and get three points.”
The best of the stats
- This will be the first competitive meeting between Leicester and Zorya Luhansk.
- Leicester will be facing Ukrainian opposition for the first time in Europe, whilst no English team has ever lost to a side from Ukraine on home soil (P32, W25, D7).
- Leicester will become just the second English side Zorya Luhansk have faced in European competition having lost home (0-2) and away (0-1) to Manchester United during the 2016-17 Europa League group stages.
- Leicester remain winless in the UEFA Cup/Europa League (P4, D1, L3), though this is their first appearance in the competition since 2000-01 – the Foxes are one of 77 sides to have played four or more games in the competition without ever winning.
- Zorya Luhansk have lost five of their six away Europa League games (W1), failing to score in each of those defeats.