Mauricio Pochettino believes Tottenham's recent goalscoring exploits caught up with it in a shock 3-1 defeat to Wolves on Saturday.
Spurs beat Everton 6-2 and Bournemouth 5-0 ahead of the match at Wembley, but they could not build on Harry Kane's first-half opener before Willy Boly, Raul Jimenez and Helder Costa all scored in a stunning turnaround after the break.
And Pochettino thinks fatigue from a busy Christmas schedule kicked in for Spurs during an uncharacteristically poor second period.
"We conceded the first goal and in the last 20 minutes it was tough for the team to find energy to be competitive or to try to win the game," he said.
"Of course, we started to feel it a few minutes before we conceded, which is why we were ready to add a fresh player like Oliver Skipp to help the team and we couldn't because we conceded in the action before we were going to make the change.
"I think the game was under control in the first half, maybe it was easier than we expected in the first half to dominate the game and to play so easily. They played so deep, chasing us and we didn't concede one chance.
"But in the second half maybe we started to feel that the game was over and when you start to feel the game is over and you play in the way that you play, you start to decide in a wrong way. We started to play too many long balls and then it was difficult to recover the ball and to play more with your heart than your head and we started to expend a lot of energy.
"Then when you need the energy in the end you miss that.
"We dominated in possession and in good parts of the pitch, but we missed the freshness to kill the game. That's the difference with the Everton and Bournemouth games, that we killed the games and then we managed the game properly.
"Today, when we conceded the first goal, the team was down and they started to feel the tiredness, the fixtures, and everything was against them and it was difficult to find the energy to come back.
"[I'm] very disappointed like the players, but nothing to say. Some games can happen with this type of result and we need to move on and be sure that we are ready for the next game."
The result halted a five-match winning run for Spurs, which had seen them climb to second in the Premier League, behind Liverpool but ahead of Manchester City.
"We dropped a little bit in our energy. That can happen," he added. "That can happen to us, it can happen to Wolves, to Liverpool, it can happen to Manchester City.
"That is why it's so tough to win the Premier League, because you need to be consistent, and today for us it's a clear example [of what happens] if we are not consistent enough.
"With not only good quality during the game, and the right energy, it's difficult to compete for big things."
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