Dundee made an impressive start to the season and blew away Killie 4-0 on the opening day but form has taken a dip in recent weeks.
At the weekend, they found themselves 2-0 down after 48 minutes, Josh Magennis heading the visitors in front early on and Steven Smith firing an unstoppable shot from 25 yards just after the break.
Rhys Healey pulled one back for Dundee with a looping header but it wasn’t enough, and Hartley insists the only way they will correct things is by getting back to basics on the training ground ahead of next weekend’s trip to Inverness.
“We’ve got to pick ourselves up,” the Dundee boss said. “We can’t make out that we were anything but flat. It’s hard to explain why we were like that because we weren’t expecting it.
“Now it’s about moving on and our next game is away to Inverness. We’ve got to make sure we get a good result up there. The only way we’ll get it right is by putting the work in on the training ground.”
Meanwhile, Kilmarnock counterpart Gary Locke is sure his players won’t get carried away with their recent run of fine form, which has seen them win four of their last six matches.
“This is all down to the boys,” he said. “But we can’t slacken off and that won’t happen. The lads are realistic enough to know that.”