Tigers have lost six of their past seven games in all competitions since action restarted in mid-March after a hiatus to accommodate the Six Nations.
Before that, they won nine of 12 games to give them a shot of a treble of trophies.
“Since the Six Nations we hit the brakes,” McKellar said.
“After 23 weeks on the bounce, we built quite a bit of momentum and for whatever reason, and we will dig and find out, we haven’t got it right since then.”
The Australia, who previously said he endured the most difficult moments of his coaching career in the days after Leicester’s Premiership hopes were brutally ended by Bristol earlier last month, said Tigers have done “a lot of learning as a group”.
“It’s a new coaching group, I’m new to this club, new to this competition, and as I’ve said in the past, things I do well is I’ll listen and adapt and I’ll make sure we are not sitting here in eighth position in 12 months’ time,” McKellar said.
To do that, however, he said every facet of the campaign, starting with preseason, will be analysed.
“Our physical preparation, our preseason, was hard and we probably went too hard too early,” McKellar said. “And did we peak early and burn the players out?”
McKellar has also started discussions with the club’s hierarchy about what he will need to try and improve Tigers’ fortunes next season.
“We’ve had many conversion around what is required, because there are some things we have had to cope without that have made life pretty difficult,” he added.
“The club has been supportive and understand that. We will make sure we have a full deck of cards from a coaching and starting perspective for next season.
“I pride myself on running a programme that is world class and for whatever reason we haven’t been able to do that this season.”
