Mauricio Pochettino was trying to remain positive after his Tottenham side were beaten 1-0 at home by West Bromwich Albion on Sunday.
The north Londoners were edged out by James Morrison's 74th-minute header at White Hart Lane to suffer their second defeat of the season and the performance was nowhere near Pochettino's lofty standards.
Spurs produced just one shot on target throughout and were sloppy for most of the 90 minutes as Alan Irvine's Baggies recorded their first victory of the campaign.
Pochettino told Spurs TV: "It was difficult. It was our fault. We played very slowly at the start and afterwards it was difficult.
"I am very disappointed. We need to analyse why. We had a very bad day.
"We need to fix it and focus on the next game."
Spurs, who dropped to ninth on the Premier League table, next take on Nottingham Forest in the Capital One Cup on Wednesday night before taking on Arsenal in the north London derby next weekend.
