The Lilywhites are effectively already out of Europe having suffered a 6-0 defeat in the first leg in Bulgaria last week. That thumping has come in the middle of a bad run for the side who topped the table for much of the first half of the season.
Foster is hoping that a good display against Levski can help turn their season around once more.
“The players will learn a lot from playing against a team of this standard,” he said.
“The mood in the camp is very good. We need to just take stock of where we are at.
“We are not going to get too disheartened. Last week we lost to the top seeds in the Europa League but we are working hard and we know we need to defend much better.
“This time two years ago Dundalk were in the First Division. We need to take the experience of European competition and learn from it,” he said.