Steve Bruce lamented Newcastle's defensive shortcomings but was left particularly flummoxed by the awarding of a penalty which he feels proved a "big turning point" in West Ham's 4-2 victory.
Efforts from Callum Wilson and Jacob Murphy were cancelled out by Aaron Cresswell and Said Benrahma as West Ham twice fought back from a goal down to leave both sides' Premier League season-opener finely poised after an hour.
The decisive moment came after 63 minutes when Michail Antonio's header clattered the bar and ricocheted into Murphy, whose attempt to claim the loose ball led to him being adjudged to have upended Pablo Fornals in the area.
While Antonio's spot-kick was saved by Freddie Woodman on his Premier League debut, Tomas Soucek bundled in the rebound. Three minutes later Antonio put the game to bed as the Hammers started their campaign with a flourish.
Bruce admitted Newcastle must improve at the back but questioned why referee Martin Atkinson did not go to a nearby television monitor to check his decision to award a penalty.
"It's the big turning point in the game," said Bruce, who revealed his intention to have a conversation with Atkinson to better comprehend his understanding of the issue.
"In the Premier League, it's fine margins. Once we went chasing the game we made it very difficult for ourselves.
"Why didn't the referee have a look at the monitor rather than someone else 300 miles away? If he'd have done that after looking at what I've seen four or five times he might have turned round and said 'that's a bit harsh'.
"But defensively, unfortunately, we gave away too many soft goals. It's getting that balance right. As soon as we chase the game then we left ourselves exposed and open, we simply can't afford to do that at this level."
There were boos from the 50,673 in attendance, but Bruce was delighted with the first bumper crowd at St James' Park in nearly 18 months.
"Let me tell you, I've said it since we've had empty stadiums how much we've missed the supporters and the support," he said.
"The spectacle for me has not been the same since the crowd's not here. But a big well done to them. To have over 50,000 is quite remarkable."
It has been a frustrating summer window for Bruce although his ranks were swelled with the permanent addition of Joe Willock, who was not registered in time to play in this fixture after being signed from Arsenal on Friday.
On the prospect of more incomings, Bruce added: "We'll keep monitoring to see what we've got, see what becomes available but at this particular moment I'm delighted that we've got Joe Willock in.
"We'll see if there's anybody who can make us better and if there is then we'll try. My job is to improve us, so all over the pitch we look at so that's what we'll try and do."
David Moyes ushered West Ham to a surprise sixth-place finish last term and Europa League football. While they twice fell behind in the first half, the Scot never doubted their resolve in an entertaining contest.
"I thought the fighting spirit was there in the first half," said Moyes. "I thought the football performance was excellent all-round.
"It was a really good game, if you were a neutral you would have said it was a good game of football, plenty of action at both ends.
"I thought we had good control of the game at different times, we kept the ball well, at times we had to suffer a bit when we didn't have the ball. But I thought in the main we deserved to get the victory."
