Giovanni van Bronckhorst bemoaned Rangers' failings against "immense" Champions League opponents after another hammering at Napoli edged them closer to an unwanted record.
Rangers have shipped 19 goals in the Champions League this season, the most in a single group stage by a Scottish side, after a 3-0 dismantling by in-form Napoli in Group A on Wednesday.
Van Bronckhorst's side have lost five straight games in Europe for just a third time, with this being their first such sequence in a single campaign.
But Rangers could hit a new low with defeat in their final group outing against Ajax, entering that match with a goal difference of -18.
Dinamo Zagreb hold the worst group-stage record in Champions League history, pointless and with a -19 goal difference in the 2011-12 campaign.
Van Bronckhorst has repeatedly called on his side to learn in the face of high-quality opposition, and he echoed that message after yet another humbling in Naples.
"You can't imagine the opponents we are facing. We think about our performances, of course, but we have to be realistic," the Rangers manager told BT Sport.
"The level we are facing in this group is immense. You have to be ready for 90 minutes – I think the moments we created in the game, we should have taken.
"In too many games we are conceding too many goals. You want to compete at the highest level. It is tough, I said that when we qualified, but you want to be here.
"The more you play it, the more experience you will have as a team and as a player. It's a competition we want to keep competing in. You have to start well in an environment like the one we faced today.
"The two goals we conceded in the first 15 minutes, we are two against one in the centre against one striker. For us to give those goals, it's too easy.
"The reaction we showed afterwards was very positive. We had a big moment to score just before half-time. In the second half, we showed character, we were well organised and tried to push for the goal.
"We created some big moments, but if you don't take those moments in these kinds of games it is difficult to win."
Rangers host Ajax on Tuesday, when they must avoid defeat to avoid claiming at least a share of unwanted history.
Van Bronckhorst added: "[The Ajax game] is a chance to get our first points. We want to leave the tournament with our heads held high, and it's another chance to play at home."
