England Under-21 coach Stuart Pearce says Joe Mattock has "stepped up" ahead of Tuesday night's friendly against Poland U21s at Molineux.Pearce has highlighted Mattock's emergence in the England U21 squad as an example of ill-discipline having a direct effect on a player's international career.

Leicester defender Mattock is in Pearce's squad to face the young Poles in Wolverhampton (kick-off 7pm), but he only got his chance to impress when Ryan Bertrand was sent home for breaking a curfew with the under-19s last October.

Bertrand, the Chelsea defender who is currently on loan at Norwich, was considered to be ahead of Mattock in the pecking order but paid the price for returning late to a training base along with Scott Sinclair and Andy Carroll.

Sinclair had also been suggested as a possible U21 candidate but has not been invited into Pearce's squad.

Pearce said: "Not so much Sinclair. You might look at Bertrand, who was in that category. I had Joe Mattock step up who was behind him in the U19s.

"I speak with the U19s manager and he tells me who is available for selection and who isn't. Joe stepped up in that respect."

Following a week where players' conduct on and off the pitch has been under scrutiny, Pearce insisted there would be no special instructions for his players abide by.

Pearce was at White Hart Lane last week when the issue of discipline came up following Ashley Cole's disrespect towards referee Mike Riley, and he feels there needs to be changes in attitudes towards officials.

The U21 coach has been stunned at how players put pressure on the referee.

"At this moment in time, the amount of people crowding around referees is not acceptable," Pearce said.

"People are arguing about decisions that are clearly the right decisions, that is the most frightening thing.

"We have to make sure we stamp that out. That starts with every individual player turning around and playing his part.

"In general it's crept into our game. One thing is for sure, something probably has to be done to address that and give the referees a little bit more respect.

"When I was manager at Manchester City the message was always put across. After games I made it my point not to criticise referees. We all have to take that lead and try to make their job that little bit easier."

Pearce, though, feels it is a problem at club level, rather than at international.

"I was always fully aware that representing your country was the next step up so your conduct had to be spot on with your club anyway," he said.

"At international level, if your conduct's not right, the chances are you won't get picked in the squad anyway. So I think it's important right across the board that your conduct's right.

"It's not something that Fabio (Capello) has turned round consciously and said we have to do right through the age groups but he'll have a code of expectation within his squad; I do with this squad and other national managers will be the same."

Pearce's attitude towards officials stems from his time playing under the late Brian Clough, who never stood for dissent towards referees from his players.

"He made it abundantly clear that you had let the side down," Pearce said.

"He never wanted you to talk back to a referee - he wanted to do that himself."

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