With Slovakia and Romania meeting in the other game, Sydorchuk said his team know a win will see them through to the last 16 as one of the top two, but he did not want to tempt fate.
"When you say something very loudly, the echo will be very loud as well, so I think we should be silent and we should do what we can do, and we'll see tomorrow at 21:00 CET what we could do," he told reporters on Tuesday.
The Ukrainians, who bounced back from a 3-0 defeat by Romania to notch a 2-1 win over Slovakia, face a Belgium side who started the tournament losing to the Slovakia, but have quality experienced players in their squad.
Midfielder Sydorchuk, who plays in Belgium for Westerlo, said he wanted to thank the Belgian people for the reception he and his family had received since moving there.
"The first time in school with my kids, in the supermarkets and the markets, everybody is kind to me. I want to say thank you for that, but my family will support just Ukraine tomorrow, sorry," Sydorchuk said with a smile.
Coach Serhiy Rebrov said he wanted to see his side qualify to alleviate some of the misery caused by the Russian invasion of his homeland.
"What will it mean for the country is that we will go on with this fairytale, this really fantastic fairytale for several more days for the whole country, because we are at war for almost 900 days," the 50-year-old coach said.
"For the Ukrainians, every game, every event like that means a lot, it means for them that they can come back to the usual pre-war times."