The Premier League champions sit in eighth place on the table and have already lost five times this season.
Skipper Van Dijk said in his match programme notes: "We went into the recent international period with mixed emotions, I would say. Disappointment, for sure, at the manner in which we lost at Manchester City, but also encouragement at what came before that, with important, hard-fought and deserved victories over both Aston Villa and Real Madrid.
"We don't shy away from the truth at this club. We know that there is improvement to be found in our performance levels, and we know that the only way to find that improvement is through hard work and togetherness.
"I have said many times that I believe in the quality and the character of this squad, but we have to show it where it matters, which is out there on the field.
"We know what lies ahead over the next few months, but for now our focus must be on the next game only. We fight for the win, we fight for the three points and we go from there."