LEE CATTERMOLE has issued a stark message to any Sunderland players still uncertain about whether they want to be part of Simon Grayson’s rebuilding job at the Stadium of Light: “You know where the door is.”

Sunderland’s squad has been subjected to a radical overhaul since the end of last season, but further changes could still be in the offing with the transfer window not due to close until a week on Thursday.

Lamine Kone and Wahbi Khazri continue to be linked with big-money moves away from Wearside, while French side Lyon have expressed an interest in taking Didier Ndong back to Ligue 1 after his strong start to the Championship season.

Cattermole could yet be offered an opportunity to return to the English top-flight, with a number of Premier League sides having courted him in the past, and Darron Gibson’s outburst ahead of the opening weekend of the campaign suggested some Sunderland players were actively looking to engineer a move away from the North-East.

It hasn’t looked that way in the opening three league games, with Kone and Ndong in particular making major contributions to the Black Cats’ unbeaten start, and Cattermole is happy with the strengthening team spirit that has become increasingly apparent in the last few weeks.

However, with the transfer deadline approaching, the skipper is adamant there is no place for anyone whose commitment to the cause is wavering.

“Everyone’s attitude since the first day we came back for pre-season has been spot on,” said Cattermole, who is set to retain the captain’s armband for tomorrow’s home game with Leeds United. “That’s what we’ve drilled into everybody – this is how it’s got to be to get out of the division.

“If you’re not willing to show the right attitude, then the door’s there, but everyone’s doing the best they can and hopefully we’ll get the rewards.

“There’s a bit of honesty, and the way we’re working together as a group has got us our results so far. Sometimes it won’t be pretty, but at home we can maybe expect a bit more of a high-tempo game and get the fans off their seats a bit.

“It won’t always be like this, but we’ve come to some difficult grounds and you’ve seen big clubs struggle in this league, so we’ve got to be pleased with where we’re at.”

This is Cattermole’s 12th full season as a professional, but it is the first time he has found himself plying his trade in the Championship.

He claims the opening three games have not been too much of a surprise, with the Championship having a long-established reputation for competitiveness, relentlessness and unpredictability.

In many ways, Wednesday’s 1-1 with Sheffield Wednesday was a perfect encapsulation of what the Championship is about, with Sunderland dominating for more than an hour, but still finding themselves holding on for a point in the closing stages as their opponents rallied.

So many of the Championship’s teams are extremely closely-matched, and that is why an ability to dig in and remain competitive – a mind-set that Cattermole tends to epitomise - can often be a crucial asset.

“There’s no mass difference in quality between the teams, and you get honest teams who work really hard, and you’ve got to keep matching them,” said the Teessider. “I don’t think your quality is going to allow you to dominate teams – there are always going to be real 50-50 games, so you’ve got to be level-headed.

“The problems start when you think you’re a bit too good for the division. If you see where we were last season, we’ve approached the games in the right manner, not walked around with a swagger. We probably deserve to be here, so it’s up to us to get ourselves out of it.”

Sunderland’s unbeaten start has dispelled at least some of the doom and gloom that enveloped the club throughout the majority of last season, and there is a palpable sense of anticipation ahead of tomorrow’s game with a Leeds side that have also made an unbeaten start.

There is plenty of history between the two northern clubs – not least thanks to the 1973 FA Cup final – but with Sunderland having spent the last decade in the top-flight, it is 2006 since Leeds last visited Wearside for a league game.

The Black Cats won 2-0 on that occasion thanks to goals from David Connolly and Grant Leadbitter and were promoted at the end of the campaign, and while it is far too early for anyone to be getting ahead of themselves this season, Cattermole is happy to help cultivate an air of anticipation that has been absent for far too long.

“As a group we’ve got to make sure we don’t get carried away, but I’m all for the fans getting excited and enjoying themselves,” he said. “If you look at the amount of games we’ve won in the last five or six years, it’s not many. Let them get excited so long as we as a group respect every team we play and be aware of their strengths.”