Atletico's 1-0 win over city rivals Real Madrid on Saturday maintained their 100 per cent start to the new Primera Division season and they sit alongside Barcelona at the top of the table.
While Barca's 'tiki-taka' approach has been adopted by most teams in Spain, Atletico's success has been based around organisation and defensive discipline.
Fonseca said: "I consider Atletico an Italian team in a Spanish championship.
"They are very deep when they defend, but they are also very balanced.
"We have to be a team which manages all the moments of the game without losing that balance.
"Also, we need to have lots of patience to find the spaces which are almost non-existent in their defence."
Fonseca admits Atletico present a sizeable upgrade to the opposition they face domestically.
"Each game has difficulties, and this team will pose us problems to solve, problems that we do not have in our championship," he added.
"We know the importance of the home games, and it is very important for us to win our next two matches here in order to have a comfortable margin to face what's left of the group."
Atletico make the short hop across to Portugal with confidence sky high following their first league win over Real since 1999.
As well as their domestic form, Atletico also claimed victory in their Champions League opener against Zenit St Petersburg to leave them top of Group C heading into the second round of fixtures.
Things could hardly be going better for Diego Simeone's men, but captain Gabi knows they cannot afford to take their foot off the pedal.
"We are going to take it step by step and not relax, that's when things go wrong," he said.
Gabi also hailed striker Diego Costa, who has helped Atletico overcome the loss of star striker Radamel Falcao this summer with eight goals in the opening seven league games, including the winner at the Bernabeu at the weekend.
"He is a very important player for us, he is indispensable to the team, the team knows what he wants. He is growing as a player and is vital to us," Gabi said of the Brazilian striker.
Costa, who played for Portuguese side Braga earlier in his career, will not be involved on Tuesday however as he completes his two-match European ban for his dismissal against Viktoria Plzen in last season's Europa League.
Fellow striker Adrian Lopez is also still absent as he recovers from facial surgery but defender Diego Godin has been named in a 20-man travelling squad.