If they beat Belgium, you could definitely go into the matchup with Spain relaxed and feeling like you’re playing with house money and content with whatever happens (although a competitive game within a goal would be really nice to see).
I don’t think a lot of casual soccer fans have true context of how hard it to beat a truly superior team in the World Cup. The better team is going to control possession most of the game. It usually takes the perfect storm of events — great goalie play along with numerous near misses and other luck that just keep a game at 0-0 or 1-1 and then keeping it there until late and hoping to be the first one to break through.
Kind of like Cape Verde tying Spain.