STEVE Caldwell has claimed that the strength of Sunderland's midfield could be the crucial factor in maintaining the club's surge up the Championship table.

Last weekend's 1-0 win over Norwich extended the Black Cats' unbeaten run to five games, and took Roy Keane's side to 13th place, their highest league position of the season.

The Irishman's decision to switch to a 4-5-1 formation has created an extra spot in the middle of the park, but the likes of Dean Whitehead and Tobias Hysen have still been unable to establish themselves in their preferred midfield roles.

Caldwell admits that the competition for central places is more intense than in any other position at the Stadium of Light.

But while there will inevitably be winners and losers as Keane begins to settle on his preferred starting line-up, the skipper insists that Sunderland can only benefit from the strength in depth.

"There are very few sides in this division who can claim to have a midfield that is anything like as good as ours," said Caldwell, who was the victim of Keane's rotation himself earlier this season.

"The competition for places in there is so intense that it's driving everyone on to bigger and better things.

"All of the midfielders know that, if they have one bad game, they could find themselves out of the side for three or four months at a time.

"As a defender, you're obviously concentrating on making sure that your own game is right.

"But there have been times recently - especially in (last week's) win over QPR - when some of our passing really stood out.

"We have players in this team who are really comfortable with the ball at their feet and, as a team, it's up to us to make the most of that kind of ability."

Meanwhile, Danny Collins has claimed that the poor state of the Stadium of Light pitch is hindering his team-mates' attempts to play a passing game.

Saturday's win over the Canaries was blighted by a number of misplaced passes, but Collins feels the uneven playing surface was at least partly to blame.

"It was a scrappy game," said the Wales international. "It was as difficult to play in as it must have been to watch.

"We would all love to play slick, pretty football, but that's not always possible. I have to say that the pitch isn't helping us at the moment. I don't know what's happened to it, but the pitch is very bobbly and it doesn't make things easy."