The Crows were outplayed by a fired up Demons unit at Adelaide Oval and trailed by 36 points in the second term before a second-half fight back.
Crows coach Brenton Sanderson criticised the structure of his forward line after the game, and Jenkins conceded the enthusiasm needed to compete at the highest level wasn't there early in the match.
Jenkins, who on Monday re-signed with the Crows for two years, was unable to explain why, particularly given the club's starts had been a talking point in the lead up to the game.
As important as it was to understand what went wrong against the Demons, Jenkins said it was crucial the side focused on the future as it tried to keep its season alive.
"Much like the team, we were a little bit flat to begin with, we didn't quite have the energy that I think we've had the past fortnight," he said.
"That's something we need to have a look (at) … effort shouldn't be something that's manufactured.
"We started poorly against the Dogs and we made it an emphasis that we wanted to start well [against Melbourne] so I felt like the group was ready to go – evidently that wasn't the case.
"The reality is that we've got to get on with it, otherwise one poor loss will turn into two or three."
The game was further soured by the loss of forward Tom Lynch with a broken jaw and defender Matthew Jaensch to suspected broken ribs, ruling them both out of the club's round nine game against Collingwood.
Lynch will be difficult to replace, given his remarkable running power for a key forward.
Jenkins said the expected return of Taylor Walker to the senior side after Adelaide's bye this weekend will help, describing him as the attack's "spiritual leader".
Walker booted four goals in the SANFL at the weekend in his second game back from a knee reconstruction.
Although Jenkins predicted Walker's return would offer a psychological boost to the side, he warned the superstar's inclusion wouldn't guarantee a win.
"He's an organiser and he's an orchestrator of everything we try and do and he's the vocal and spiritual leader almost of the whole group," he said.
"To get him back in terms of his presence is going to be amazing, and whatever he can bring performance wise will be a bonus.
"It's going to be unfair on him to expect him to win the game games for us in the near future, but just having him out there will lift a lot of the guys for sure."
Twitter: @AFL_Harry