Joe Hart's mistake in West Ham's 1-1 Premier League draw with Stoke City came as a surprise to manager David Moyes.
Hart failed to gather a shot from Xherdan Shaqiri and was second to the rebound as substitute Peter Crouch pounced to put Stoke in front at London Stadium on Monday.
Andy Carroll's volley salvaged a point for Moyes' men but Hart will be in the spotlight after a second mistake in four games since being restored to the West Ham team.
While the goalkeeper impressed in a 1-1 draw at Chelsea, Hart was at fault for one of Burnley's goals in a 3-0 home defeat last month.
Hart appears set to be included in Gareth Southgate's England squad for the World Cup despite playing second fiddle to Adrian for much of the Premier League season.
And Moyes accepted he did not expect Hart - on loan from Manchester City - to be at fault as relegation-threatened Stoke took the lead.
"He had two very similar shots in the first half," Moyes told a news conference. "So it was a surprise that it spilled out. If you're a goalkeeper, it's going to happen [mistakes].
"I said after he made great saves at Chelsea 'well done'. Just like tonight, I'll tell him he should have done better."
West Ham have taken five points from their last three matches and sit seven points above the relegation zone, but Moyes is not convinced his side are assured of a place in next season's Premier League.
"If you get to 40 points, then it'll be close," the Scot said. "We want 40."
