Vicente del Bosque's side added the world crown to their European title when they beat the Netherlands 1-0 in South Africa in July.
They will launch their bid to defend their position as European champions at the Rhein Park in Vaduz before going on to face Argentina in a friendly the following Tuesday.
Spain will be expected to win at a canter on Friday against a team who have never qualified for a major finals, although their record has improved in recent years.
Busquets is adamant they must concentrate on the qualifier rather than look to the meeting with Argentina who reached the quarter-finals in South Africa before being destroyed by a rampant Germany.
He said: "The friendly against Argentina is very exciting but first is the Liechtenstein game which is important. We are playing for three points and we have to start well in Euro qualifying."
Spain started poorly at the 2010 FIFA World Cup, going down to a 1-0 defeat by Switzerland before improving throughout the tournament and enjoying a deserved victory.
The 22-year-old midfielder insists the players must put their achievements behind them, adding: "Winning the world title should now be over. It will go down in history and now we must start again.
"When we lost to Switzerland we were not the worst and now we are not the best nor do we believe we are invincible. When you get successful people take many things for granted."
Striker Fernando Llorente, who played just one match in South Africa, echoed Busquets' sentiments, saying: "The important thing is to forget the world title and start from scratch. There are new challenges and we must work with humility."
The defender has earned close on 100 caps for his country and Busquets bemoaned his team-mates absence. "Puyol is very important here and to get 100 games is a significant number," he said. "We hope he recovers as soon as possible."
As well as taking on Liechtenstein, Spain will face the Czech Republic, Scotland and Lithuania in Group I.