Stoke boss Mark Hughes admits he spoke to his players specifically about the issue of grappling at set-pieces ahead of Monday's 4-0 loss to Tottenham.
Defenders holding attackers while marking them in the area was a major talking point from Sunday's 2-2 draw between Leicester and West Ham, with a number of instances during the contest coming under scrutiny.
There was then a notable lack of such cases in the game at the Britannia Stadium on Monday, only one involving Potters skipper Ryan Shawcross and Spurs' Toby Alderweireld standing out.
Hughes feels Stoke have suffered unfairly in the past when the matter has come to the fore.
And, speaking at his news conference to preview Saturday's trip to Manchester City, he said: "We did mention [before the Tottenham game] we needed to be careful as a consequence of the focus on that particular aspect of set-piece work.
"We needed to be careful and make sure we didn't get caught out, like we have been in the past.
"We have suffered when there is a spotlight on this issue. We've had games following a little bit of noise about grappling and almost without fail suffered the consequences -- wrongly on most occasions in my view, with us seeming to be the only ones getting penalised for it on that weekend.
"Then it goes away again for a few months and you wait for the next time."
Hughes believes there needs to more clear guidance on the issue.
"It's always been prevalent, and the powers that be on occasions have a purge, a couple of months where they stamp down on it, but then it reverts back and there is a certain level of acceptance," the Welshman said.
"I recall they did try to clarify a couple of Premier League manager meetings ago, trying to explain what would be penalised and what would not.
"I think the gist was if the guy impeded was likely to head the ball in, it's a penalty, but if it's just general 'grappling' and the ball flies over everyone's head, it's not. That was my understanding then, but whether or not it has changed, I don't know.
"Everybody is a little bit in the dark and there is too much grey area to it. I think the message needs to be repeated on an ongoing basis, because I think people forget what is allowed and what isn't."
He added: "We say to mark correctly. My view is you can defend space or players. We expect our defenders to mark individuals, making sure they don't score or get first contact.
"But it is difficult for officials. I wouldn't like to be a referee having to sort out the mess of a penalty area when a ball is coming in."
Hughes also revealed winger Xherdan Shaqiri (hamstring) will miss Saturday's match, and that 40-year-old goalkeeper Shay Given, who made his first Barclays Premier League appearance for Stoke on Monday, is set to keep his place.
Meanwhile, the Potters have announced their ground is to be known as the bet365 Stadium from the start of next season.
Stoke have entered into an initial six-year stadium naming rights agreement with the betting firm that owns the club.
It was also announced the gap in one corner of the stadium is to be 'filled in' in time for the 2017-18 season, creating 1,800 extra seats and lifting the capacity above 30,000.