Defender Ciaran Brennan who has previously played for the nation of his birth at both under-18 and under-19 level, was brought into the squad for the first time for matches against their counterparts from Switzerland, Australia and Denmark.
The 21-year-old was due to make the trip to Spain to take part in the fixtures, but revealed on social media he was having to miss out because of illness.
He wrote on Instagram: “Gutted to miss out through illness. Good luck all the lads, honoured to received my first u21 call-up.”
The call-up is the latest in a long line of successes for Brennan, who impressed on debut at Rochdale in the EFL Cup and played a starring role against Premier League opposition when they faced up to Everton in the FA Cup a few weeks later.
He has made four appearances total since his arrival on the scene and is highly thought of, having had his contract triggered into a further year by the club last week.
Brennan is one of a number of exciting Owls youngsters hoping to impress Darren Moore in pre-season after the Hillsborough boss intimated they would be given every chance to play their way into his thinking as he seeks to forge a new way forward for the club.
The Wednesday youngster would have joined former Owls Conor Grant, who was sold to Rochdale in February, in the under-21s squad.