
Allardyce left the club in January after only 24 matches in charge, since when Newcastle have failed to win any of seven league games and have slipped towards the relegation zone.
Last week midfielder Damien Duff claimed the squad had got fitter since Kevin Keegan took charge, but Allardyce has angrily dismissed his suggestion.
"There wasn't anything wrong with match fitness when I was there," he said. "That's a bit of an excuse. Sometimes fitness is a mental thing.
"The fear factor can drain an awful lot out of players so that may be the problem at the moment. There is also a lack of confidence and it can boil down to that, not a lack of match fitness," he insisted.
DPA