Young defender Reece James was drafted in on loan from Manchester United in the summer, but he too was sidelined due to a thigh injury.
"When you look at the age group of the team which started the game, it was always going to be difficult," Abbott said after Saturday's surrender.
"This is going to be my toughest season by a long way because of the thinness of the squad.
"We need to be injury-free and we need our senior players to be playing every week.
"It's even tougher now than it was two weeks ago because we've lost two games far too heavily. We have to find a way to deal with it.
"It's not about making excuses because we were just too young and fragile.
"We need everyone in our squad to be fit and available or we're going to find it hard.
"We had too many young boys who are still learning their trade and you do get found out when that's the case."
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