Roberto Martinez believes Everton suffered from the elation of beating Manchester United last weekend in Saturday's 3-2 Premier League defeat at Aston Villa.
Everton ran out comprehensive 3-0 winners against United at Goodison Park last Sunday, but they fell well short of that standard at Villa Park.
The Merseysiders were particularly underwhelming in the first half as two goals from Christian Benteke put Villa 2-0 ahead.
Romelu Lukaku scored from the penalty spot in an improved second-half showing, but Villa earned a big win in their fight against relegation as Tom Cleverley's 64th-minute strike took the game away from Everton and rendered Phil Jagielka's injury-time goal a mere consolation.
"The intensity we had in our last game against Manchester United maybe made it difficult to start at the same level," manager Martinez said.
"I was a little bit worried about exactly what happened, of coming here and not having the stimulation after having such a big performance and result and atmosphere at Goodison last weekend.
"Sometimes it can be difficult away from home. I thought having fresh legs and players would bring something to the side and it would help us.
"It wasn't the case and we got heavily damaged defensively. You're not going to be perfect every game."
Martinez was happy with his team's response after the break, but conceded the first-half display left Everton with too much to do.
The Spaniard added: "First half we were second best in everything we did even in the way we kicked the ball, reacted to second balls, defended with poor intensity in our box.
"Villa were the best side in first half, we were better side in second half, but we couldn't get through the poor period without being too damaged."
