Nottingham Forest lost for the first time under Barlow and Ian McParland as they went down 3-2 at Victoria Park to relegation-threatened 'Pools.
"Complacency was not a factor today, the game was too competitive to be complacent, Barlow told the club website.
"In attempting to get hold of the game we were second place in areas we have been dominating in the last seven or eight games."