Rangers manager Philippe Clement says his side "threw away three points" after an "unacceptable" first half in Paisley led to a 2-1 defeat by St Mirren on Boxing Day.
The Ibrox club are now 12 points behind rivals and leaders Celtic, who they welcome to Ibrox next Thursday for the second Old Firm derby of the league season.
Oisin Smyth opened the scoring for the hosts from the penalty spot before Danilo grabbed his fourth goal in six matches to equalise in the second period. Substitute Caolan Boyd-Munce then won the game for the Buddies with a magnificent driven effort in injury time.
"I'm very disappointed about the result and about our level in the first half," Clement told Sky Sports News.
"We threw away the three points today ourselves. In the first half, we didn't show enough quality on the ball, but we also lost a lot of duels.
"I didn't see that one coming after the consistency that the team has shown the last two months. But we made some changes, and the team reacted in the second half.
"We missed points ourselves by not showing the level in the first half that we needed. The first half was not acceptable.
"We need to focus on ourselves because we don't have control over how many points our opponents get. It's about us taking the maximum points."
Later in his press conference, Clement added: "We cannot play like we played in the first half, that's below the level
"It's below par for everybody in the team. And that's not the mentality you can accept at Rangers. That's why I was so angry at half-time also.
"We had enough chances after that goal also to score more. Of course, you need to take a lot of risk in the last 10 minutes. And in that way, you get a second goal against.
"But we dominated all the second half. We had the ball all the time. Even in the first half, we had the ball. We didn't do enough with it.
"They didn't give it in the first half, that's clear. We lost the game there, that's why I was so angry at half-time also. We played far below our level in every sense, on the ball, without the ball, in the duels, in movements, in everything."
St Mirren's first league victory over Rangers in almost exactly 13 years lifts them to fifth in the Scottish Premiership table and leaves them one point better off than they were at this stage last season.
"We were terrific in the first half," St Mirren boss Stephen Robinson told Sky Sports News.
"We pressed Rangers really aggressively and had numerous chances. The never-say-die attitude has to be admired… we've had our trials and tribulations off the pitch.
"To be sitting in fifth place, a point better off than we were last season is testament to this group. I take my hat off to them and I believe there's more to come.
"First and foremost, (the goal is to) stay in the league. We're a club that doesn't get ahead of ourselves. This group of players have the potential to do that (qualify for Europe) again, but we have to keep our feet on the ground."
