ALAN Pardew felt goalkeeper Jak Alnwick was left “exposed” at the Emirates Stadium.
Alnwick made his full debut in Saturday’s 4-1 Premier League defeat to Arsenal.
The 21-year-old played in the absence through injury of Tim Krul and Rob Elliot.
And United manager Pardew felt he was let down by those in front of him.
“Jak has to prove he is a goalie, and a top goalie,” said Pardew.
“I did think he wasa little bit exposed. We’ve not really defended as a unit a well as we have done in the previous games, particularly Chelsea. We need to re-establish that.
“Maybe we took too many risks in trying to get something out of the game, and therefore you are going to expose your defenders and your goalie.
“We can’t afford to do that.”
Asked if the result had affected Hexham-born Alnwick’s confidence, Pardew added: “No, I can probably look at one goal as Jak maybe at fault.
“The second, he might have wanted to stay in his goal a bit longer without coming out. Other than that, I thought he was pretty sound.
“A few times it flashed across, and he got little touches.
“He kicked it well, looked assured. I can’t lay any blame at his door for this result, and he goes to the next game.”
Newcastle return to North London on Wednesday night for a Capital One Cup quarter-final against Tottenham Hotspur.
And Alnwick – who is out of contract next summer – will be in goal for the next half a dozen games.
Pardew said: “This is a guy who has got in a short period of time an opportunity to make a big name for himself, and he’s the sort of guy you would want to do it.
“He’s a good honest guy, humble, and another local. So fingers crossed he does well.”
Asked about a timescale for the return of Krul and Elliot, Pardew said: “I don’t think they will be back until mid-January – it’s a long wait.”