Captain Mats Hummels claimed Borussia Dortmund have yet to "confirm that we really are back" despite starting the Bundesliga season with a 4-0 win.
After reaching the winter break last season in the relegation zone, only to recover and finish seventh, Dortmund's emphatic opening to the 2015-16 Bundesliga against Borussia Monchengladbach made fans and pundits alike sit up and take notice.
Henrikh Mkhitaryan scored a brace as Thomas Tuchel's men thumped Gladbach on Saturday but Hummels was quick to underline that consistency will be the key, if Dortmund are to avoid a similar performance to last term.
"We've got to confirm that we really are back. Last year, we had six points after three games and everything seemed to be fine," he said, according to the Bundesliga's website.
"Then we threw the game away in Mainz when we really shouldn't have and suddenly nothing was working anymore.
"We know very well that two or three good results don't mean much yet. We want to keep it up over 34 matches of the season, and preferably also in the DFB Cup and the [UEFA] Europa League.
"We're heading in the right direction but there's still a long way to go. You can soon drift away if you just drop a few per cent."
Dortmund's next match will be away to Odd in Norway in the UEFA Europa League play-off first leg, while they face a trip to Ingolstadt in the Bundesliga on Sunday.
But after tearing apart Gladbach - who finished third in the German top flight last season - Hummels agreed that Dortmund's best can trouble just about any team in the world.
"If we play to our full potential, as we did most of the game against Gladbach, then we know that we can play like this," the defender said.
"Our aim is to do that regularly. We want to dominate as many games as possible and make sure we're not reliant on luck or misfortune."
