Last season Liverpool defied expectation by getting to the final of the Champions League, only to lose following Loris Karius' infamous display and Gareth Bale's incredible first goal. Red Star remain bottom of the group but are now on four points.
A first-half double from Milan Pavkov was the difference for the home side with the Serbian striker's long-range effort in the 29th minute a standout.
"That's the thing, not taking the chances when we're creating them".
Klopp's side were beaten 2-0 by Red Star in Serbia in what was their second away defeat in Group C.
Mohamed Salah fired over the bar shortly afterwards to sum up a poor first half for Liverpool, with Daniel Sturridge also missing an early chance for the visitors when he volleyed over the bar from close range. They were, if you want, on their bikes and we had to deal with the situation.
"I think it made sense to make a few changes, a few we had to make and a few we wanted to".
Milan Pavkov scores twice as Red Star Belgrade stun Liverpool
Their passing was sloppy, their midfield was ill-disciplined and they seemed to lack any sort of clear game plan. That's what we want to do and that is why I made that decision".
It may be a little harsh as Lallana was excellent for Liverpool during Klopp's early years at the club but a succession of injuries have taken their toll and it remains to be seen whether the England worldwide will be able to return to his best form. The second goal was kind of out of the blue, we had the ball and gave it away.
And it has ultimately left Liverpool with real work to do in their final games away to PSG and at home to Napoli. At half-time we walked a long way to the dressing room and they were all in a very positive mood.
Back then, eastern European teams were genuine contenders for club football's biggest prize - Steaua Bucharest of Romania were European champions in 1986 - and Red Star had some of the world's best players like Robert Prosinecki and Dejan Savicevic.
Red Star moved onto four points, two behind Liverpool, and their home form means they still has a chance of a top-two finish. Arsenal are 1/3 to win the match and that looks a fair price but an Arsenal win and more than 2.5 goals to be scored must be considered at 5/6.
Asked if Liverpool FC's performances had dropped in recent months, Klopp replied in his post-match news conference on Tuesday night: "In the game [yes], not in general". They deserved it for the passion they showed.