"That's what happens when little boys play big games," Allen joked on the Swansea website. "As long as I can get back for next season I'll be happy."
Injuries and the Championship play-offs could severely limit Wales' midfield options at the Stadion Gradski Vrt.
Manager John Toshack, who is due to name his squad next Thursday, expects to be without long-term injuries Aaron Ramsey and Jack Collison until next year.
The 22 May Championship play-off at Wembley takes precedence over the Croatia match and there are Wales internationals in the squads of all four semi-final contenders.
Cardiff City have Joe Ledley, Adam Matthews and Darcy Blake in their ranks, while their opponents Leicester have the in-form Andy King.
Rob Earnshaw and Chris Gunter feature for Nottingham Forest whose play-off opponents Blackpool have Neal Eardley, David Vaughan and Rob Edwards in their ranks.
Wales captain Craig Bellamy is also unlikely to be considered for the Croatia trip as he is expected to be visiting his footballing foundation in Sierra Leone.
Source: BBC Sport
Source: BBC Sport