A surprise 2-0 defeat to Italy on matchday one has left Marc Wilmots' side needing a favourable result against Ireland in Bordeaux to keep qualification for the Euro 2016 knockout stages firmly in their own hands.
Long scored 13 times in an impressive season for Southampton and is expected to lead the line for Martin O'Neill's side when they take on Belgium, having played the full 90 minutes of the 1-1 draw with Sweden.
And Courtois is wary of the threat posed by the diminutive 29-year-old, telling a news conference on Friday: "At first sight, Shane Long is just a short striker, but he's good in the air, he's quick, very dangerous, has good feet and scores goals.
"It's hard to compare him to Lukaku, [Christian] Benteke or [Michy] Batshuayi but he is at that level. We'll have to keep an eye on him.
"We know what to expect from Ireland, they will fight for every ball, every metre. We have to have the same intensity. It will be a hard game but if we play well then we should win. We have to win.
"We know the attributes we have and we'll show that. We've seen that there aren't any easy games, games being won late on, and it'll be a tough match. We're rightly favourites but we need to play with the right focus and come away with the win."
Belgium were heavily criticised for their performance against Italy, despite dominating possession, but Courtois insists that more of a cutting edge in attack is all that is needed to change their fortunes.
"I think if we're at our best level then people say we're one of the best, but if you lose then suddenly you're the worst. That's football, it's always like that," said the Chelsea man.
"Things were quite good against Italy, one goal was a shame as it was an individual mistake but Italy didn't have many other clear-cut chances.
"We're all winners. I was a little frustrated after the match, perhaps we didn't do what we needed to do but hopefully we've learned the lessons. We have to be more sharp in the box, we were sometimes lacking that in the few friendlies before the Euros started.
"I think we were well positioned tactically but people didn't do their jobs at times. We discussed it internally and things will go well tomorrow."