Chasing 165 to strengthen their playoff chances, RCB were dismissed for 134 in Jaipur, finishing the season with six wins and eight defeats.
"Too much batting stress on just AB de Villiers," Kohli told Star Sports after the game. "I thought we were in a great position at one stage. We were 75 for 1, the way we were bundled out after that wasn't ideal.
"A guy like AB, who has the ability to hit fours and sixes, was knocking it around. We needed more smart decision-making there and guys were just not up to the mark and that is disappointing to see. It's not something that should be repeated by five, six guys in a row. One or two guys is okay, but the others should have applied themselves and that wasn't the case tonight."
RCB were cruising at 75 for 1 in the ninth over, with de Villiers batting fluently. Then the middle order imploded against legspinner Shreyas Gopal, trying to play expansive strokes even though the asking rate was not out of control.
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Over the years, RCB have relied heavily on their top three batsmen. Without Chris Gayle this season, Kohli and de Villiers shouldered the run-making responsibility and scored 530 and 480 respectively. The next best among the middle-order batsmen was Mandeep Singh with 252 runs. Sarfaraz Khan made only 51 in six innings.
"We wanted to strengthen the middle order that hasn't been our strength for the last few years," Kohli said. "It's something we need to look forward to in the next season. We need to be more smart about how we compose our team, I guess.
"The bulk of the scoring responsibility and stress can't always be on a guy like AB all the time in the middle order. Guys need to step up at the right times. We certainly want to take up the responsibility but there have to be contributions at important stages. One occasion was tonight where AB scored runs, apart from him others didn't show enough composure."
Most of the positives Kohli picked out were in the bowling department, which Umesh Yadav led by taking 20 wickets.
"Quite a few new players came in and performed well," Kohli said. "Umesh was outstanding, Chahal was good with the ball as well, Siraj took his opportunities. Moeen contributed and gave us the balance. We have a few positives that we can take forward to the next season, but it feels disappointing to not finish this game off."