Erik Pieters believes Newcastle United will cause many more problems from set-pieces this season.
Pieters was in the Stoke City side beaten 2-1 at St James's Park on Saturday.
Jamaal Lascelles powered a header in off the crossbar from a Matt Ritchie corner in the second half to claim all three points.
Lascelles had scored the only goal of the game against Swansea City six days earlier – again a header from a Ritchie corner – and Pieters and his team-mates had watched videos of the strike.
But Stoke's zonal marking system gave Lascelles an edge.
And one-time United target Pieters said: “It’s frustrating.
"Set-pieces are such a big part of modern football. There’s always a chance you can get beaten by a set-piece, and there's always a chance you can score from them.
"We have to be honest with ourselves and look at that one today and make sure we don’t concede many more like that.
"But it wasn’t just the goal, it was how they got the corner, that was sloppy from us as well.
"And then of course we didn't defend the corner properly either.
"We’ve been watching videos of Newcastle and then we concede an identical goal to theirs last week.
"We had said to each other we know they come like that and set ourselves to be zonal for the set-pieces.
"We know they’re going to be strong in that area, but still we have to make it as difficult as possible when they come charging in and we didn't.
"We gave him a free header and you can’t do that.
"We felt comfortable in the second half and when we scored we thought we could go on and win the game.
"We had some chances to do that but we didn’t take them and then a set-piece was our downfall and we know how important they are in modern football."
Meanwhile, United captain Lascelles is looking to score more goals.
The 23-year-old believes it's easier to score from set-pieces in the Premier League.
"I don’t think I’ve scored two so early on, but Matt Ritchie’s delivery is just so good," said Lascelles, whose mum revealed on Twitter after the game that she used to give her son £5 for every goal he scored when he was an Academy player at Nottingham Forest.
"In the Premier League, it’s a little bit different because in the Championships it’s more of a wrestling match in the box.
"Players will get hold of you and they’re big, strong boys and they defend set-pieces well.
"In the Premier League, no disrespect to teams, when they mark zonal you can get a running jump.
"Last week (against Swansea), I managed to get myself into a good area and I was disappointed I didn’t score in the first half.
"I should have done. But it’s something we’re working on. I’d like to aim higher."