While the Reds did improve their performance in the second half of the game, they were unable to get all three points.
A Mohamed Salah double had given them a 3-2 lead, but Fabian Schar gave the Magpies a late equalizer.
"It was all about the players (at half time)," Van Dijk said to reporters.
"I had a few things to say, others did as well but we all know how it works in football, you still have plenty of time to turn it around. At 1-0 you have to do so many things differently.
"You can talk about tactics but it begins with winning battles, winning duels, winning 50/50 challenges and second balls, putting them under pressure and in the second half we showed that but unfortunately it wasn't enough to win it.
"What was lacking? Challenges. We know when we play here they have an extra...I don't know what happens to them but the fans feed them, they win their challenges, the fans feed off that as well.
"We were not good enough, not good at all then they create momentum, we don't, we lose the ball too easily at times, sloppy in possession and they make momentum. We had 50 minutes to put it right, which we did but unfortunately we couldn't get it over the line.
"I think everyone was disappointed. It was 100% two points lost. To concede in the last couple of minutes - and the way we conceded - was very disappointing."
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