Swansea City Under-21s all-but booked their place in the Professional Development League play-offs as Joe Thomas grabbed the only goal to beat Birmingham City Under-21s at the Swansea.com Stadium.

Full-back Thomas turned in a corner in stoppage time at the end of the first half, and it proved enough to settle a tight contest against a Blues side already assured of a play-off spot.

There were some nervy moments during the closing stages, with the Swans knowing only a win would be good enough to extend their season, but they saw the game out to continue their 100 per cent record at the stadium over the past two seasons.

The development side will now face Sheffield United – winners of the northern section – in the semi-finals, barring the unlikely event of Bournemouth winning their final game of the season with a 14-goal swing in the Cherries’ favour.

Coach Anthony Wright had made two changes from the victory over Sheffield Wednesday, with Thomas and Joel Cotterill coming in for the suspended Filip Lissah and Glory Nzingo respectively.

The Swans started brightly, Kyrell Wilson winning the ball high up the field and delivering a dangerous cross that Ben Lloyd could not direct goalwards.

Birmingham responded, Menzi Mazwi’s low shot drifting just wide of Evan Watts’ left-hand post.

Bradley Mayo in the Birmingham goal held a Cameron Congreve shot from Aimar Govea’s cutback, before Watts got down sharply to deny Tommy Fogarty.

Birmingham came forward again, counter-attacking sharply to set up Junior Dixon, but the white shirts were back quickly to crowd out the Blues forward.

Swansea responded in kind, getting forward in transition through Wilson, who teed up Mitchell Bates, but the midfielder’s low strike was parried by Mayo.

Congreve tricked his way past two defenders, but ignored Govea in support to take on a shot that Mayo gathered in, before the Swans took the lead right on the stroke of the interval.

Thomas was left unmarked and needed no second invitation to turn home Lloyd’s inswigning delivery.

Lloyd almost gave the Swans the perfect start to the second period after releasing a superb shot from distance which was tipped onto the crossbar by a full-stretch Mayo as the keeper pulled off a stunning save.

Watts was then called into action five minutes later, keeping out Benjamin Wodskou’s close-range effort after another quick counter-attack from the Blues. 

Wilson was continuing to cause problems at the other end, and delivered dangerous crosses that Lloyd and Govea could not steer home.

As time ran down Birmingham pressed forward in numbers, and Watts did well to parry Dixon’s rasping effort, while O’Shea Ellis saw his follow-up blocked by Thomas.

Josh Home then fired wide for the visitors before Cotterill lofted an effort over the bar following good work from Wilson as the Swans secured the three points required to effectively set-up a semi-final against the Blades.

Swansea City Under 21s: Evan Watts, Joe Thomas, Josh Carey (Sebastian Dabrowski 72), Joel Cotterill, Iestyn Jones, Kian Jenkins, Cameron Congreve, Mitchell Bates, Kyrell Wilson, Ben Lloyd (Glory Nzingo 72), Aimar Govea.

Unused substitutes: Remy Mitchell, Thomas Woodward, Kai Ludvigsen.

Birmingham City under 21s: Bradley Mayo, Femi Olofinjana (Callum Sullivan 46), Tommy Fogarty, Laith Fairnie, Rico Browne, Josh Home, Junior Dixon, Benjamin Wodskou, Frank Tattum (Benjamin Beresford 72), Menzi Mazwi, O’Shea Ellis.

Unused substitutes: Oliver Sayer, Cameron Eubank, Zachary Willis.