Attacking midfielder Jonas Hofmann started for Klopp's men on Saturday, while striker Marvin Ducksch and playmaker Milos Jojic each came off the bench in the second half.
It was Jojic who had the biggest impact as the Serbian found the net with a deflected strike after Havard Nordtveit had been sent off for Gladbach, who had earlier taken a two-goal lead with strikes from Raffael and Max Kruse.
The defeat leaves Klopp's side 23 points adrift of Bundesliga leaders Bayern Munich, who will clinch a second successive title next weekend if they win and Dortmund and Schalke fail to do so.
"Marvin Ducksch proved with little time how much of a threat he can be," Klopp said.
"Milos Jojic showed what he is capable off for us and Jonas Hoffman managed to make a mess of the ball on two occasions which slightly startled him but in the second half he was fully there and played a good game."
