Derek McInnes says Rangers shot themselves in the foot and beat themselves after throwing away a precious early lead in Bialystok.
McInnes' side went one up after just four minutes when Jagiellonia defender Guilherme Montoia turned Tuur Rommens' cross into his own net.
But just nine minutes later it was level, and after a further eight they were behind, with the defending leaving a lot to be desired for Kajetan Szmyt's double.
The Rangers manager says his team stopped doing what was working for them after going ahead, were broken on too easily and, ultimately, beat themselves with mistakes.
He told BBC Radio Scotland: "I felt we beat ourselves. We started the game really well and in absolute control. The team was picked to make sure that the rotations in midfield weren't a problem, and they weren't.
"Our three did fine in there at times. We got off to a good start with a good bit of combination play, being patient with what we were trying to do, and putting stress on their defenders. We scored an own goal and it was a perfect start.
"Then we stopped doing what was working for us. We made two mistakes for the two goals. I’m not going to watch us all season lose the ball on the edge of the box and have it end up in a chance for the opposition.
"We need to be far more concentrated, focused, aggressive, talkative, and organised to stop these types of things happening. We saw a lot tonight of what we were last season. We gave up too many chances and gave teams too much encouragement."
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It's not all doom and gloom for the former Hearts boss, with the performances of half-time substitutes Findlay Curtis, Nico Raskin and Cammy Devlin giving encouragement.
"There are positives," he added. "The substitutes did well; Findlay, Nico, Cammy, and Vanya came on.
"We didn’t throw the kitchen sink at it because it is a two-legged game and we feel there is another big performance in us at home next Thursday. We were giving teams too much encouragement, and we are guilty of beating ourselves tonight.
"That is no disrespect to our opponent because transitions and counter-attacks fuel them. They have pacey wide players who get up and down the pitch quickly. From a physical aspect, we looked fit and strong, and we had good chances in the second half. We should be doing better with those, but I am more concerned about the amount of chances we are giving our opponent. It has to change."
McInnes still wants further additions in the transfer market and was asked if this performance highlighted that need.
He said: "Yes. It doesn't help that Ben (Godfrey) gets injured. It doesn't help that Makhanya hasn't played 90 minutes since the back end of May. We are trying to get him up to speed.
"Sometimes you make signings in the window who have not been playing games. Daisuke has not had any real minutes throughout preseason, but we took a gamble because we needed that type of player tonight.
"We have reasons for where we are, but we still have work to do. It is collaborative; we are all together to try and bring the specific players we need to the club, both in an attacking and a defensive sense. The squad will look different when the window closes. While we are getting there, we have to be winning games. You are judged on winning games. I am hopeful we will win the tie."
