The Zambian, who spent three years playing in the Jupiler Pro League with KV Oostende before moving to Glasgow last summer, reckons the Belgian side will provide tough opponents after narrowly missing out on the title last term.
Sakala admits he watched the Brussels outfit earlier this season and spoke to a number of his former team mates about Union before the draw was made.
The 25-year-old, who featured in victories over Brondby, Sparta Prague, Red Star Belgrade, Braga, RB Leipzig and Eintracht Frankfurt last season, believes Giovanni van Bronckhorst’s side will avoid an early exit from the competition.
He said: “Union were in the lower league in the time I was there, but I have watched some of their games in the Belgian league even though I had left and they are a good side.
“But we are ready for them. This team we are going to face have just come from the Second Division and they almost won the league. They’ve topped the league and lost in the play-offs.
“I have had conversations with my friends in Belgium about them, especially when they were top of the league. We talked about them before the draw and before we kne we were facing them, so I knew a lot about them.
“I did the right thing to watch them a little bit because I have an idea about how they play. Honestly, at the time I wasn’t looking for their weaknesses because I didn’t know we were going to be facing them.
“Looking at the journey we had last season, everyone s expecting us to win this game easily. That is something that us players are focused on - we have to win.
“I believe we are going to do it because our target is to play in the Champions League this season. That is the dream of each and every player.
“The team is looking very exciting, even better this season. It was amazing to play against such good teams in the Europa League last season, but Rangers are one of those big teams.”
Union have been forced to play the first leg away from their home ground due to the Stade Joseph Marien failing to meet UEFA requirements and Sakala reckons the change of venue to the nearby Den Dreef will aid Rangers’ cause.
He added: “I feel it is an advantage for us that the have changed the venue because they are obviously more comfortable in their own stadium.
“Both sides will be going to a place we are not used to. It will be a 50-50 situation, but we are Rangers so we are always thinking about winning.”
Union Saint-Gilloise winger Dante Vanzeir reckons his side have nothing to lose in Europe.
The 24-year-old, who came through the youth ranks at Belgian rivals KRC Genk, refused to count his team out of the qualifier.
Speaking to HLN earlier this month, he explained: “It’s a great team. We have to be one hundred per cent ready.
“At home we go all out for that victory. If you can keep the zero on the move... we have nothing to lose in Europe.”