There would have to be several injuries for that to happen.
1. David, Larin, Buchanan, Davies
2. Millar, Hoilett, Brym, Cavallini, Ugbo
3. Nelson, Shaffelburg, Corbeanu, Bair JR-R
Then there's the never been called up:
Colyn, Kerr, Kulenovic.
He's gotta be doing better than he is. A lot of guys are at similar levels and have had a better season/performing better.
I will say I miss the 3 game windows. It brought a unique aspect to international football where rotating/using the entire squad was inevitable.