The Black Cats were beaten 3-1 by Barclays Premier League newcomers Norwich at the Stadium of Light to leave Advocaat scratching his head and disgruntled supporters urging chairman Ellis Short to invest heavily in the remaining weeks of the summer transfer window.
Advocaat, who will hold a grisly post-mortem on Sunday, said: "Even this squad must be good enough to get a better result against Norwich with five new players, but there is something wrong, that's quite simple.
"I have an idea about it, but tomorrow we will have a meeting and they can talk and I will talk.
"What was so wrong was I saw players playing - and I don't want to mention names, it was the whole team with the exception of one or two players - and they did things that I don't expect from a player at this level.
"I have to know why that can happen because it's really strange for me
You can play badly and badly, but not knowing what to do is even worse."
The visitors assumed control, if in slightly fortuitous circumstances, with 26 minutes gone when Costel Pantilimon parried Robbie Brady's shot against the shins of Russell Martin and saw the ball roll into his net, and full-back Steven Whittaker doubled their advantage eight minutes before the break after playing a neat one-two with the excellent Wes Hoolahan.
Victory was all but assured within 12 minutes of the restart when Hoolahan was once again the pivot for Nathan Redmond to make it 3-0 with substitute Duncan Watmore's late strike providing scant consolation.
Asked about Watmore's late cameo, Advocaat said: "He did in 10 minutes more attacking-wise than some others, but again, if you start as a regular, it's a different way of playing
But he did well."
Opposite number Alex Neil was delighted with the efforts of his players as they extended their remarkable record of never having lost an away game since his appointment in January.
He said: "Last week because we played well, if you go and back that up with another good performance but no points, then you start to question are we good enough? But the performance and the result today showed that we are more than capable of holding our own at this level.
"Those three points, we will gain a lot of confidence from that and hopefully go into the game next week and hope to replicate how we have been playing."
Asked about the Canaries' success on the road since his arrival, he said: "I'm not quite sure, it's not something I've really thought about.
"We set out to win every game
Some teams go away from home and will be happy to take a point; we go away from home and we want to win the game, and we have done that more often than not since January."
Source : PA
Source: PA