Guernsey FC manager Tony Vance admits he got a "couple of calls wrong" as his side were beaten 2-0 at Hastings.
It was their first defeat in 10 games and saw them drop to fourth in the Isthmian League Division One South.
"Unfortunately the performances of a lot of our players, and us as coaches as well, wasn't quite there.
"Our possession was poor, really sub-standard, that's what's disappointing because it was a superb pitch," Vance told BBC Radio Guernsey.
"Everyone has a bad day at the office and maybe I got a couple of calls wrong as well, to be fair, so we've all had a bad day."
Guernsey may be without midfielder Tom de la Mare for some time after he had to go off with an injury.
"I think the worst thing is it's his knee and ankle," added Vance. "We're not sure of the severity of it but it didn't look great and he's playing on a groin injury as well."