City beat Barcelona 3-1 in the Champions League on Tuesday in what was their first win over the Spanish side.
City beat Barcelona 3-1 in the Champions League on Tuesday in what was their first win over the Spanish side in six attempts.
The victory was lauded as a landmark result by City manager Pep Guardiola, the former Barcelona boss, following his pre-season arrival at the Etihad Stadium.
However, Belgium international De Bruyne, who scored from a free-kick against Barca, is wary of complacency creeping in ahead of the Premier League leaders' match at home to Boro.
"The game against Middlesbrough is going to be another tough test," De Bruyne said.
"Obviously everyone will talk about Tuesday because it was Barcelona, but if you lose at the weekend it doesn't matter what happened in the Champions League.
"We have to do the same as we did in these two games and try to win against Middlesbrough to go into the international break with a good series and try to maintain top spot in the league.
"It is very difficult. Everybody will give everything they have got against us. We have to do what we know how to do."
City are quickly adapting to the methods introduced by Guardiola and look a more formidable side than under his predecessor Manuel Pellegrini.
De Bruyne claims the transformation under Guardiola has not been a radical one, though, and believes it is the former Barcelona and Bayern Munich coach's ability to focus on specific things which has been most beneficial.
"It's not like Guardiola has changed a lot," explained the 25-year-old. "Football is still football -- but it's his eye for detail that counts."
City captain Vincent Kompany will press his claims for a return to the starting line-up in defence as he edges closer to full match-fitness.
Guardiola remains without right-back Bacary Sagna (hamstring) while midfielder Fabian Delph is still recovering from a muscle injury.
Meanwhile Middlesbrough forward Alvaro Negredo has been backed to rediscover his goal-scoring touch as he prepares to face his old club for the first time since leaving 18 months ago.
Negredo claimed Premier League and League Cup winners' medals during a two-season spell at City following a transfer from Sevilla in 2013.
However, the 31-year-old has struggled to reproduce the kind of form that brought him 23 goals in 49 appearances for City since returning to the Premier League following a loan move to Teesside from Valencia.
Negredo has failed to find the net since the opening-day draw against Stoke City in August, but Middlesbrough team-mate Antonio Barragan has faith in his ability.
"Alvaro is one of the best strikers out there," Barragan said. "He's in a good place right now, and he knows how to score goals.
"In my opinion he's still good enough to be playing for one of Europe's top sides."
Despite a 2-0 FA Cup win at the Etihad Stadium at the start of 2015, Middlesbrough have not won away to City in the league for more than a decade.
Head coach Aitor Karanka has been forced into at least one change due to Uruguay midfielder Gaston Ramirez serving a suspension.
Marten de Roon, Cristhian Stuani, Grant Leadbitter and Viktor Fischer are on standby to come in as northeast side Middlesbrough look to extend their unbeaten run to three consecutive games.