Former Tranmere defender Luke Waterfall could become Chris Wilder’s ninth signing of the summer, should a trial prove successful.

Wilder is looking to add a centre back and the 18-year-old, who was released by the League One side last season, could fit the bill.

Waterfall, who has been given a week’s trial, began his football career as a youngster at Barnsley, before switching to Tranmere in July 2008.

Wilder said: “He’s a young lad who was recommended to us.

“We have got Kevin Sandwith who can play at centre half, but we need back-up or a player to put pressure on Luke Foster and Mark Creighton.

“When I came to the club last year we didn’t have strength in depth, but now we do.”

Meanwhile, Wilder says his players will have every chance to stake a claim for a first-team spot ahead of their Blue Square Premier opener against York on Saturday, August 8.

United yesterday announced their squad numbers, with goalkeeper Billy Turley named No 1, and new signings Mark Creighton, Jack Midson and Dannie Bulman included in the first 11.

But Wilder said the numbers on the shirts would have no bearing on his first-team line-up.

“I think it’s irrelevant,” said Wilder as the players returned for their first full pre-season training session at their new Chesterton base.

“Everyone will get a good chance at it. We’ve got 19 to 20 players that can play a part in the season, so it’s going to be a squad effort.

“It’s a long, long season and you are going to get injuries, illness and loss of form, so we need competition in all areas of the squad and that’s what I believe we have got.

“But we can’t play them all at one time and the players will have to buy into that.”

Defender Chris Carruthers, who was made available for transfer at the end of last season, is No 23.

Wilder explained: “No one has shown an interest in taking him, so he will take a full part in the pre-season while he is an Oxford United player.

“At the moment, it’s all about getting the players fit in time for the start of the season.

“If a player has a bad pre-season then he’s not going to get in the side.

“But I’m confident that we have players with the right sort of character and that’s something we check whenever we are keen to sign anyone.”

Wilder stressed that pre-season was structured to ensure that the team would be at peak fitness when the big kick-off arrives and free of injury.

“By the time the season starts, I want all the players to be knocking at the door,” he said.

Meanwhile, Wilder has yet to decide who will be captain this season.

Wilder said: “Adam (Murray) was captain last season, but they have to get in the side first.

“I want players to take responsibility for their actions, I don’t want people to leave it to whoever is wearing the captain’s armband.

“It’s all about the players taking collective responsibility.”

U'S SQUAD NUMBERS

1 Billy Turley 2 Damian Batt 3 Kevin Sandwith 4 Dannie Bulman 5 Luke Foster 6 Mark Creighton 7 Adam Chapman 8 Adam Murray 9 James Constable 10 Jack Midson 11 Simon Clist 14 Marcus Kelly 15 Alfie Potter 18 Alex Rhodes 19 Shane Killock 20 Sam Deering 21 Ryan Clarke 23 Chris Carruthers 24 Matt Green 27 Richard Groves 28 Ian Sampson 29 Declan Benjamin