Why one of the unsung heroes of Sunderland's play-off charge could be facing his biggest test yet this week

Sunderland's season has already surpassed all expectations and if they were to make it to Wembley for the play-off final, they will have to overcome their biggest test yet.

Tony Mowbray's defensive options were already threadbare even before the final-day trip to Preston North End, with Danny Batth, Aji Alese, Niall Huggins and Dan Ballard all sidelined.

With no natural centre-forward fit, it has left Mowbray's side acutely vulnerable from set pieces and it almost proved their undoing when Watford scored from their only two corners of the game at the Stadium of Light.

After the wins at both West Brom and Preston North End, Mowbray made a point of singling out goalkeeping coach Alessandro Barcherini for praise. Barcherini takes a significant role in preparing the side for defensive set pieces and has been tasked with finding imaginative ways to compensate for Sunderland's extreme lack of height. It has given the goalkeeping coach sleepless nights and the work has been a key factor in the team's impressive unbeaten run since the international break in March.

Sunderland have deployed a variety of different techniques, at times moving away from their usual hybrid system of zonal and man-marking to flood the area around Anthony Patterson and hopefully maximise the chances of a red-and-white shirt making first contact with the ball.

Mowbray has also talked about working with the players individually to try and help them find ways to mitigate against the height advantage their opposite number will almost certainly have over them.

While the head coach has been asked about leaving some of his own players high up the pitch, potentially taking some opposition threats with them, he feels that creating extra space in the box will work against his side. Denying the opposition space to attack the ball is seen as vital to getting through the current injury crisis.

The challenge for Sunderland is that far from easing, their defensive injury crisis could yet get worse for the first leg at the Stadium of Light. Dennis Cirkin was replaced at half time at Deepdale after a firm challenge left him with a heavily swollen ankle that he could not move, while Lynden Gooch was later replaced as a precaution.

Sunderland face an anxious wait this week to see if Cirkin's issue will settle, while Mowbray was hopeful that Gooch will be available. The 27-year-old may not add much to the side in the way of height, but his tenacity and competitiveness is vital.

January signing Joe Anderson will be on standby, but at this very early stage of his career Mowbray has made clear that his strengths are in possession - as evidenced by his composed cameo in the latter stages at Deepdale.

The head coach remains hopeful that he may have the choice to gamble on Ballard, but that is dependent on the defender making a successful return to training this week.

For a side lacking natural defenders, Luton Town are a daunting opponent. Carlton Morris and Elijah Adebayo are an impressive strike pairing, while the side's three central defenders also pose a major threat.

In Sunderland's favour is their vast array of outstanding attacking talent, but their success will depend on how they manage to defend their own box. There may be another sleepless night or two for Barcherini this week.