"He was sent off for a two-footed tackle and I'm very frustrated for him," Foyle told the Stoke Sentinel.
"It's a part of his game that we've been talking about for ages, but the penny hasn't dropped yet.
"He's a decent kid and we wanted to get him out on loan to get experience and help him develop.
"He's out for three weeks and we'll have to see what happens now and whether Cambridge will want to take him on loan again."