AND so we wait.

The most worrying setback for Sunderland at the weekend was not Joe Edwards' late goal for Plymouth after Anthony Patterson's parry but the sight of Dan Ballard hobbling away from Home Park in a protective boot and on crutches.

It hadn't been the most memorable afternoon for Ballard, who scored an own-goal and then conceded a penalty, but his Sunderland importance can't be questioned and a lay-off so soon after Aji Alese was also ruled out would be a major blow for Regis Le Bris and the Black Cats.

Hopefully it doesn't come to that. There's not yet been confirmation on whether the prognosis is positive or negative, with Le Bris set to speak to the media on Thursday afternoon ahead of Saturday's visit of Middlesbrough.

But setbacks are why squad depth is so crucial and suddenly the Chris Mepham signing has the look of being one of the shrewdest bits of Sunderland summer business.

Waiting in the wings is a player with Premier League and World Cup experience and, aged just 26, a player who will feel his best years are still ahead of him. And while he hasn't played a minute of club football so far this season, he played all 90 for Wales in the win against Montenegro this month.

Saturday is a big game and there's bound to be a rip-roaring atmosphere at the Stadium of Light but Mepham, if called upon, will take it all in his stride.

"It's a big club with a huge fanbase, as a player you want to play in those atmospheres," said the Bournemouth defender when he joined on loan.

His know-how and experience would come in handy as well.

"It's a very young team which is amazing to have so many young players," he said.

"But with that there might be a little bit of inexperience. I can bring experience, I've played in World Cup matches and Premier League games. I can bring a calm head. I'm looking forward to playing in front of the amazing fanbase and doing great things here."

Mepham headed for Sunderland with no intention of settling for a role as a squad player.

Having lost his place in the Bournemouth side last season, the former Brentford man had no plans to allow another season to pass him by as a spectator. And now in the final year of his contract with the Cherries, this is a crucial loan spell at Sunderland.

He's playing for his future - be it at the Stadium of Light or elsewhere.

"I am probably - in football terms - coming to the peak of a career now at 26," said Mepham earlier this year.

"The next couple of years are important for me. It's important to play week-in-week-out."

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There is someone else to consider here: Leo Hjelde. The former Leeds United man enjoyed an impressive pre-season and will perhaps feel unfortunate to have not yet kicked a ball in the Championship this season.

The 21-year-old sees himself as a centre-half rather than a left-back and will have been waiting for an opportunity to present itself. But that wait is likely to go on, even if Ballard is ruled out of the Boro game and beyond - for Mepham will almost certainly be the favourite to come into the side.

Options, though, is what Le Bris wants. In midfield and defence, there's depth there now, depth that is already being put to the test.

Mepham will be put to the test this weekend if he's called upon to make his debut. But he'll back himself to rise to the occasion.