Cassidy replaces Celtic’s Jonathan Afolabi (currently on loan at Dundee) who has been ruled out of the double header.
While Cassidy was part of Crawford’s training camp in Belfast in August this will be his first call-up to the Under-21 squad.
Republic of Ireland Under-21 Squad
Goalkeepers: Gavin Bazunu (Rochdale, on loan from Manchester City), Ed McGinty (Sligo Rovers)
Defenders: Nathan Collins (Stoke City), Darragh Leahy (Dundalk), Conor Masterson (Queens Park Rangers), Mark McGuinness (Ipswich Town, on loan from Arsenal), Danny McNamara (St Johnstone, on loan from Millwall), Lee O’Connor (Tranmere Rovers, on loan from Celtic), Thomas O’Connor (Gillingham, on loan from Southampton), Liam Scales (Shamrock Rovers)
Midfielders: Conor Coventry (West Ham United), Luca Connell (Celtic), Will Ferry (Southampton), Jason Knight (Derby County), Danny Mandroiu (Bohemians), Connor Ronan (Grasshopper Zurich, on loan from Wolverhampton Wanderers), Anthony Scully (Lincoln City), Jack Taylor (Peterborough United)
Forwards: Ryan Cassidy (Accrington Stanley, on loan from Watford), Zack Elbouzedi (Lincoln City), Danny Grant (Bohemians), Joshua Kayode (Carlisle United, on loan from Rotherham United), Michael Obafemi (Southampton), Troy Parrott (Millwall, on loan from Tottenham Hotspur)
UEFA Under-21 European Championship Qualifier - Group 1
15/11 - Republic of Ireland v Iceland, Tallaght Stadium, 12.30pm (Live on eir Sport)
18/11 - Luxembourg v Republic of Ireland, Beggen, 4.30pm (Irish time)