Hibernian head coach Neil Lennon admitted his side were off the pace as they suffered a surprise 3-1 home defeat by Hamilton in the Premiership.
"We have had a brilliant start to the season, and a lot of nice things said about us, and it's a dose of reality," he told BBC Radio Scotland.
"We looked very tired at the end, but that is mental, rather than physical.
"I'm bitterly disappointed with my team's performance. The better team won today. They defended better than us."
Hibs went into the match on a high after a 3-2 victory over Rangers at Ibrox last weekend had maintained a perfect start to their league campaign, while they have also reached the quarter-finals of the League Cup.
However, the display against Hamilton lacked the energy of their earlier displays.
Simon Murray headed wide of the target and Danny Swanson had a fierce drive turned around the post by Hamilton goalkeeper Gary Woods before Greg Docherty and Ali Crawford drew saves from Ofir Marciano in the home goal.
But after the break, Darren McGregor fouled Docherty in the box to allow Rakish Bingham to score from the penalty spot and Accies scored their second when Hibs defender Paul Hanlon, instead of passing to team-mate Lewis Stevenson, knocked the ball into the path of Louis Longridge, who stroked the ball into the net.
Already in jubilant mood, the small band of Hamilton fans were thrilled at their team's third goal, a slick move involving Longridge and Docherty rounded off by Bingham, before Anthony Stokes scored a late consolation for Hibs.
"I thought in the first half we were OK without being anywhere near the level which we can play at," Lennon said afterwards.
"We asked the players to increase the tempo, increase the energy but in the second half we were very, very flat.
"We didn't look secure at times today at all, people getting in the wrong body positions, the wrong positions, not giving the midfield a hand.
"Their second goal was farcical from our point of view; good players making mistakes which sometimes you can't legislate for.
"But they scored a great third goal and sometimes you have to doff your cap."
Lennon admitted to having "a wee feeling" on Thursday and Friday that complacency might affect his players after receiving praise for their performance at Ibrox.
"I don't want us to go back to playing really well against the big teams and then (losing) games you're expected to win," he added.
"We have no right to win any game here. We are the promoted team. These are Premier League teams, they are streetwise and have some quality players, and Hamilton certainly deserved to win today.
"There were one or two signs that didn't make me happy about the attitude of some of the players and the body language, but I'll learn from that."