Lee Clark questioned the desire and spirit of his players after defeat by Ross County left Kilmarnock in the Premiership relegation play-off place.
"At half-time, County looked like the team fighting for their lives, which was a real disappointment," Clark said.
"You should have so much fire in your belly that I'm struggling to keep you on the pitch in terms of your controlled aggression.
"It shouldn't be letting people have free headers in the penalty area."
Clark was not just unhappy at his players' defending for both Ross goals, but their failure to create any clear chances as they slipped to an eighth Premiership home defeat of the season.
"[We were] not good enough in both boxes," he added. "[It was] two awful goals we've given away. The situations we created didn't work the goalkeeper enough. So I'm really disappointed."
Ross County scored with their first attack, when Alex Schalk was left unmarked to head home Michael Gardyne's cross.
The substitute Brian Graham sealed the victory with a second late on, after Kilmarnock failed to clear their lines.
"We're concerned because of the position we're in and the result," added Clark. "This was a great opportunity, albeit against a good Ross County team, where we had a chance to get three points.
"[We need to] change the mentality of the players. That's three games without a goal, and take away the Motherwell game [a 2-0 win] it's five or six without a goal. Goals win you games and we need to win games, but we need to be able to defend better than we have tonight."
Victory was only the second in five league games for Ross County since they reached the final of the Scottish League Cup.
But manager Jim McIntyre does not believe the prospect of the game against Hibernian at Hampden has had a psychological effect on his players.
"Over the last two or three months it's been that way where we'd win a couple and lose a couple," McIntyre said.
"But we set out our team to attack, we knew the importance of three points. We were dominant from minute one, should have been two or three goals up at half-time, and showed the character to dig in when Killie put us under a bit of pressure.
"The disappointing thing was not to score further goals, which our play deserved. We got into some great areas and had some dangerous set-plays also, but I was delighted to get that killer second goal late on in the match. We managed the game really well."